See these sentences:

See there, it seems that someone is inside the house. OVER
See there, it seems that someone is in the house.

Another example:

The doctors found two bullets in his body. OVER
The doctors found two bullets inside his body.

Certainly, both are interchangeable, aren't they? But in the bullet's example, the second one looks natural. I'm not sure why. Is it something that bullets were first out and then they went inside? But if that's the case, someone is in the house is also okay. That person too was out first!

  • 3
    I like the first three sentences, but the fourth sounds funny to me.
    – user230
    Commented May 12, 2014 at 16:38
  • I think it's fair to say that "inside" approximately means "on the inner side of something" or "in the inner part of something", where "in" can be used in other senses (such as "in time"). Also, when both work as a noun, they are different in meaning; "the inside" still means, well, "inside", but "the in" means "influence" or "a way to get in". -- I think "doctors found something inside his body" might be less common because presumably it would happen during an autopsy, and the bullets wouldn't really be "inside" of his body anymore. Commented May 12, 2014 at 21:29
  • In my experience, in the house is preferred over inside the house. I suspect region and dialect have a strong influence over which choice sounds better given a particular nuance. Commented May 26, 2014 at 15:16
  • To add to the confusion, "within" is also an acceptable substitute for "in" and "inside" in many cases. While trying to think of an answer, I realized that "within" would be more appropriate for some sentences I was coming up with, at least for the that I imagined them having. The distinction to me seems to be very heavily based on how formal the sentence is intended to be ("inside" being more formal than "in"), although they are very interchangeable.
    – Pockets
    Commented May 27, 2014 at 20:05

8 Answers 8


Inside is strictly locative, and used where the location is enclosed. You can't be inside a field, or inside a city because the enclosure is missing.

In is locative in terms of within boundaries but is not necessarily enclosed (in the garden), and can be used for participation such as being in a club or in a race.

  • So, five liters of blood in or inside the body? Liver is the organ in or inside the body? The priest is in or inside the Church? I lost my watch in or inside the swimming pool? -- in all, in works perfectly fine. All are enclosed as well!
    – Maulik V
    Commented May 28, 2014 at 12:13
  • For blood, I would probably use in for the same reason that water is in a bottle - it is amorphous and hence contained rather than enclosed. You can't really take the blood and place it outside in any meaningful way as it would just spread out in a big puddle. I would also use in for a liver, though as the vital organs are referred to as 'insides' I wouldn't be strict about it. This is for similar reasons - livers outside the body are usually dead, so the enclosure aspect is somewhat diluted because they are not so much enclosed by the body as an integral part of it. Commented May 28, 2014 at 12:24
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    Note that I said in is not <necessarily> enclosed. Think about you priest example. If you are talking about his physical locate, he can be inside (enclosed by)or in (within the boundaries of) the church building, but if you are talking about his membership of the church you can only use in. This is why I say that inside is strictly locative and enclosed, but in is locative, but doesn't have to be enclosed, and for participation, which can be viewed as within the boundaries of a group. Commented May 28, 2014 at 12:30
  • 1
    +1 This makes sense. I'd see inside as in and side. Something in something that has sides.
    – Maulik V
    Commented May 28, 2014 at 12:53
  • Choosing this as the answer. I thought a lot of examples using both in and inside. The nuance lies in the word in there - side what you said in your very first paragraph. Thanks :)
    – Maulik V
    Commented May 30, 2014 at 5:05

We want to specifically focus on the use of in and inside as prepositions that denote location, so I'll come up with some minimal pairs.

  • He said something to guards on R'shiel's door that Brak didn't catch then went inside.
    • He said something to guards on R'shiel's door that Brak didn't catch then went in.
  • Once inside the Kalandia refugee camp, we were collected by minibuses.
    • Once in the Kalandia refugee camp, we were collected by minibuses.
  • He stood around uneasily, obviously not wanting to go back to his game of solitaire while I was still inside the room.
    • He stood around uneasily, obviously not wanting to go back to his game of solitaire while I was still in the room.

Looking at Zwarts & Winter, (2009), they seem to conflate the two for the purpose of analysing locative prepositions! Even semanticists don't seem to make a distinction between them.

Turning now to corpus data from COCA, instead of contrived examples (that's not true; the above examples are taken and derived from specimens in Collins' UK), unfortunately, doesn't give us any assistance, as there isn't yet an effective way to only search for in|inside when it's being used in a locative sense.

From what I've been able to find, there's no clear preference for in over inside, at least when referring to a location enclosed in some way - whether it is a bowl, or a ring, or any boundary, really.

The notion of grammaticality - that is, whether or not in and inside can be used alone, as a complement, à la:

  • The doctor is in.
    • The doctor is inside.

And, similarly:

  • I'm staying in tonight.
    • I'm staying inside tonight.

... is unlikely to provide useful guidance, as these examples are highly idiomatic.

It could be argued that this particular construction is permitted only because of its idiomaticity, but that's not a great solution either.

There's only one related question on ELL.SE, where the following advice is given by StoneyB:

... in formal discourse, especially if there is any possibility of ambiguity, you should use the narrower term, into or inside.

Unfortunately, I've found no convincing evidence to show that one is more emphatic than the other.

As for your specific examples: I find them all to be perfectly natural and idiomatic except for the last, The doctors found two bullets inside his body.

Forced to intuit an answer, I would say that it's to do with the indeterminacy of in as opposed to the specificity of inside:

  • A bullet was found inside his body.
    • A bullet was found in his body.
  • A bullet was found inside his heart.
    • A bullet was found in his heart.
  • A bullet was found inside his brain.
    • A bullet was found in his brain.

In each of these pairs, I find both to be equally idiomatic, except for the first two.


  • Someone was inside our house.
    • Someone was in our house.
  • Someone was in our home.
    • Someone was inside our home.

The first of each pair seems less marked, although I can't put my finger on why.

Although - there is a slight constraint on the use of inside:

  • There's fruit in the bowl.
    • There's fruit inside the bowl.
  • I jumped in the pool.
    • I jumped inside the pool.

I wouldn't expect the latter construction - the pool example is slightly more acceptable, but not by much. On the other hand:

  • There's fruit inside the open container.
    • There's fruit in the open container.
  • There's jam left inside that uncovered jar.
    • There's jam left in that uncovered jar.

In the above examples, inside works.

There seems to be a constraint on the use of inside, where it has to refer to a prototypically enclosed space - house, box, room - even where that space is opened through modification. This is probably the reason why I'm staying inside doesn't work - there's no prototypically enclosed space which inside can refer to.

Zwarts, J., & Winter, Y. (2000). Vector space semantics: A model-theoretic analysis of locative prepositions. Journal of logic, language and information, 9(2), 169-211.

  • 1
    The last two pairs of your examples left me feel unsure which one (between in and inside) is unmarked. (I guess that in is unmarked.) Commented May 26, 2014 at 15:02
  • With regards to the staying in/staying inside example, I imagine that said example is very closely related to AmE's "going out" expression, as in "Are you going out [to party] tonight?" As for the idiomatic nature of "going out", see my comment on the question.
    – Pockets
    Commented May 27, 2014 at 20:09

Technically, both forms are interchangeable in both of these examples, but you're correct that there are nuances about which one is used where.

I think the distinction here comes mainly because "inside" is usually a stronger or more emphatic version of "in". As such, "in" is usually used when the enclosing object often has things going into and out of it, and the question of what is or isn't in it might come up on a regular basis. "Inside", however, adds emphasis for situations where one might not normally expect the one thing to be inside the other, or it's not as common to consider what might or might not be inside of it.

So therefore, we would usually say that something is "in the house", but we would tend to say something is "inside his body".

There are other distinctions that sometimes come into play as well. For example, "in" can sometimes imply that something is a part that (together with other things) makes up the larger whole ("there are carrots in the soup"), but "inside" pretty much always implies that the two are distinct things, and one just encloses the other ("the filling is inside the cupcake"). "Inside" also sometimes has an implication that something is not only in something else, but that the containing object has been closed up around it, or made it harder to get to.

Lastly, it's important to note that "inside" can be used by itself when one doesn't need to specify the noun explicitly ("Fred is inside."), whereas "in" cannot.

  • 1
    I have an exception to your last sentence: “Where’s the cat – is she in or out?” … “She’s in.” Commented May 12, 2014 at 20:32
  • It's true that people do sometimes say things like that in informal speech, but that doesn't mean it's actually grammatically correct (people often say things informally that aren't correct English).
    – Foogod
    Commented May 12, 2014 at 20:59
  • 1
    Where is she? She's in. is absolutely okay! However, the speaker is just next to the door of the room, outside.
    – Maulik V
    Commented May 28, 2014 at 12:05
  • 1
    I agree with your answer in general, but that last sentence doesn't work for me, either. After all, "The doctor is in, he'll see you now," is commonly used - and a doctor's office doesn't seem like the most informal of places...
    – Alicja Z
    Commented May 28, 2014 at 18:04
  • "The doctor is in" is a special idiomatic phrase which indicates something different than physical location (it typically means that the doctor is available for consultation, regardless of where he/she is actually physically located), so it's actually not the same sort of sentiment or sentence at all. It's also generally only used in the context of consulting professionals (usually medical doctors): "The doctor is in" is common usage, "the banker is in" would be ok, but is not that common, and "the electrical engineer is in" would probably only be used in the context of joke/parody.
    – Foogod
    Commented Feb 12, 2015 at 18:38

Both 'in' and 'inside' (in these contexts) have the same meaning, but the difference between the two is emphasis, which is why one might be more appropriate than another in certain situations. Here I will ignore the other meanings for 'in' that do not mean 'inside'. (Ex: "He's in the game", 'in' here means 'to participate' or 'to be part of')

'In' is used as a general term to mean that something is within (or inside) the boundaries of something else.

'Inside', while holding the same definition, carries a slightly stronger emphasis on the fact that something is inside as opposed to outside. Because of this emphasis, it is usually used to give a sense of being enclosed completely.


  • It's in the box. (simply stating that "it" is in the box)
  • It's inside the box. (stating the same with the added emphasis or focus on "it's" location as being within the box as opposed to outside the box)

Both are interchangeable, and have the same meaning, the only difference being the amount of emphasis. Some great examples of the difference in emphasis of words with the same meaning are 'yes', 'yeah', 'yup', and 'uh-huh' (in order from strongest to weakest, in my personal perception). In this case, 'inside' is generally felt to be stronger than 'in'.

  • When something is in, you don't need to emphasize the location. In means in or inside, isn't it? How can something be more in by calling it inside?
    – Maulik V
    Commented May 28, 2014 at 12:07
  • 1
    I didn't say that it's more in. I actually said that both have the same meaning. The difference is the emphasis put on 'in' and 'inside'. Emphasis means where the focus of the sentence is, or where the implied "important part" of the sentence lays. Whether or not one needs to emphasize depends on the situation. Commented May 28, 2014 at 12:20
  • Sometimes the emphasis can completely change the meaning of a phrase. Ex: I didn't sleep with her last night. <-> I didn't sleep with her last night. This last example could be the difference between life and death. But in the end, the principle is the same. Commented May 28, 2014 at 12:26

Because 'in' has a much greater range of uses than 'inside', these associations carry over cognitively and metaphorically even to pairs of sentences in which the primary intended meaning is clear.

For instance,

It seems that someone is inside the house.

It seems that someone is in the house.

It seems to me that the second one would be the more vivid way to describe a burglary because 'in' means not only 'inside' physically but also abstractly. Compare the top two definitions of 'in' at dictionary.com:

1. (used to indicate inclusion within space, a place, or limits): walking in the park.

2. (used to indicate inclusion within something abstract or immaterial): in politics; in the autumn.

Here 'the house' can be abstract or immaterial, in terms of being understood as someone's 'safe place' or 'personal, intimate space'. Thus, there is a little bit of a connotation of personal violation that occurs with the second sentence but not the first.

Here is a different example. The Canadian Red Cross, in its blood donor campaign, has been using the following slogan:

Blood. It's in you to give.

Obviously, in this case, the Red Cross is using 'in' in two different ways: both 'inside' and 'within your capabilities/character/virtue.' The use of inside instead of in would be much less effective here.


I think the other answers are missing a bit of actual meaning.

Inside means within the container. In means within the structure.

Human bodies contain organs and blood but not the skin- the skin is the containing structure. So a bullet can be in the skin (and in the body) and but still not inside the body however if it reaches further such as the liver then the bullet is both inside and in the body.

Someone taking a role as a surgeon would be needed to remove a bullet from inside the body (it could be diverted an originally straight path or be stuck in a bone) but if it was just in the body then anyone could do it with a pincer.

The shop has a more complicated containing structure including areas like a roof space and space behind the walls. So you could in those spaces and not inside the shop. In deed, a person could stuck into a jammed door or between wall panels so a person would be in the shop but inside the shop. Inside means able to access the shop's contents- things you can buy or utility areas such as behind the register or toilets or security areas.


While thinking about the nuances between "in" and "inside", I also started thinking about the nuances between "out" and "outside" (prompted by considering the expression "going out" after thinking about the difference between "I'm staying in tonight." vs. "I'm staying inside tonight.")

What I've come up with is that "inside" and "outside" are compound words (perhaps a more knowledgeable linguist could expound on this idea) that denotes the location of the something being described with respect to the "sides" of something, sort of like

indoors, outdoors; inwards, outwards

or even better (from M-W online),

in·sid·er noun (ˌ)in-ˈsī-dər, ˈin-ˌ\ : a person who belongs to a group or organization and has special knowledge about it

out·sid·er noun \ˌau̇t-ˈsī-dər, ˈau̇t-ˌ\ : a person who does not belong to or is not accepted as part of a particular group or organization : a person or animal that is not expected to win a race or competition

The noun "insides" also tends to be quite literal, referring to the parts/components on the interior of something or, alternatively, the innards of an animal. (Neither the online M-W nor Am.Herit. define "insides" separately from "inside").

"In" and "out", however, because they lack this "qualifier" (if you can call it that) have over time become associated with various expressions and are generally much more idiomatic than their counterparts, which as the following examples show, are read rather literally when used.

Bob came in today. vs. Bob came inside today.

The latter carries the sense that Bob came indoors, whereas the former tends to be associated more closely with the expression "came in to/for work".

I'd also like to note that if you apply the "ejaculated" definition to "came", the "inside" form would be the more appropriate one to use.

The doctor is out. vs. The doctor is outside.

The "out" in the former signifies that the doctor is not currently available because he isn't present in the office and carries no connotations about where the doctor is relative to the office; it also reminds one of the expressions "out of the office" and "out of town".

The "outside" in the latter, at least to me, reads very similarly to "outside" as in "just outside the door" and "just outside the office". It seems to imply that the doctor is very close by, but isn't actually inside.

I'm staying in tonight. vs. I'm staying inside tonight.

I went out every day last week. vs. I went outside every day last week.

The expression "staying in" implies that one is not "going out", in the sense of, say, "going out to the bars", "going out on a date" or "going out to party". The "inside" and "outside" versions, however, are rather literal and are counters, respectively, to being "outside" and "inside" one's own home.

I'm eating in tonight. vs. I'm eating inside tonight.

The former implies that one is staying at home to eat - perhaps by ordering take-out or cooking for oneself; the expression has no indication about this - whereas the latter simply implies that one is eating indoors as opposed to outdoors, perhaps in the sense that instead of dining on one's terrace as one usually would, dinner will happen in the dining room.

I'm ordering in tonight. vs. I'm ordering inside tonight.

The former implies that one is staying at home tonight instead of going out to eat, and that instead of cooking, he's ordering take-out to be delivered to his doorstep. The latter implies that - at least in the context of dining (although it is a rather unique and uncommon situation) - instead of placing one's order outside the restaurant as one usually might, the intention tonight is to place the order inside the restaurant.

He's in town this week. vs. He's inside town this week.

He's out of town this week. vs. He's outside of town this week.

In each pair, the former is fairly common and is also the only appropriate way to say the expression. Although grammatically correct, there is no possible context or situation in which the latter would make sense (technically, in conversation, were "town" a proper noun, the latter expressions would be 'more' correct, although the "inside town" sentence would still be illogical).

I want in on the bet. vs. I want inside on the bet.

I want out of the bet. vs. I want outside of the bet.

Again, in each pair, only the first works. The latter expressions, as in the previous example, are not idiomatically acceptable.

Context: Imagine an oversized object, exactly one side of which is red, being moved into a house with a front entrance through which the object likely will not fit. The following sentences are being said to someone in the vicinity and aware that the object will be or is being moved indoors but cannot see exactly what is going on and knows nothing more.

The red side is in. vs. The red side is inside.

The former might be something you yell to indicate that whoever is moving the object just succesfully managed to get the red side of the object through the doorway, almost like a progress report of sorts. The latter, however, is a more cut-and-dried description and describes the state of the couch at some point in time while the red side is inside the house; it's something you might say when telling the story, as in "so picture it - the red side is inside the house, Jake's outside with a flamingo on his head...".

  • 1
    @AlicjaZ's example of "in the window" vs. "inside the window" is also very good.
    – Pockets
    Commented May 27, 2014 at 21:49
  • Could downvoters please explain?
    – Pockets
    Commented Jun 1, 2014 at 0:48
  • What @Alicja said. Arguably the stronger associations of inside with a description implying a more "distanced" perspective can be seen in "There's someone in/inside the house!", where I'm inclined to think the inside version might well be more likely if the speaker is outside the house at the time. Commented Jul 1, 2014 at 13:58

To build on what Foogood wrote, consider the following sentences:

Annie was in the window, while her sick sister lay in bed, watching their aunt in the TV.

Clara was inside the window, while her sick sister lay inside the bed, watching their aunt inside the TV.

Here, the first one sounds OK, while the second one implies a bizarre situation in which the three women are literally inside the physical constraints of the window, bed and TV - perhaps between the two panes of glass, in between the box-springs, and wedged between the liquid crystals?

Another example:

She was in the store.

She was inside the store.

Here, technically both mean the same thing, but inside puts stress on her location being within the walls of the store. In might be understood a bit more loosely (are the stalls that often stand in front of store entrances part of the store? does looking through them imply you're in the store or in front of the store?).

Now, back to your examples.

See there, it seems that someone is inside the house.

See there, it seems that someone is in the house.

While the second one sounds more natural to me (perhaps because it's quicker/easier to say), both are generally accepted to have the same meaning, since we usually talk about one way of being in/inside a house. ...That said, Alice in Wonderland could perhaps have made a distinction when she suffered a rapid growth spurt and got too large for the house she was in: if, for instance, her arms and legs started sticking out through the windows, she might say that she's "in the house, but not inside the house": that is, not fully within the confines of the house.

The doctors found two bullets in his body.

The doctors found two bullets inside his body.

Here, however, there's a slight difference in between the two:

  • the bullets in his body may have been lodged skin-deep - they were likely painful and difficult to remove, but may not have required an operation, may have been visible from the outside, etc etc;

  • meanwhile, the bullets inside his body would likely have been found during an operation, an autopsy, etc. - they're wedged inside the body, much the same way Clara's family has a tendency to be inside objects they shouldn't be.

So, the two structures allow us to distinguish between the idea that a bullet might be half-in-half-out of a body and that it was completely encased inside the body.

It's really the same case as with the house (is it fully inside or just partially in?), but we rarely talk about people being halfway in a house (Alice excepted), so we understand both the same way.

While both structures are grammatically sound, they carry with them slightly different implications:

  • in means "surrounded by something on all sides" (PEU),

  • inside means the same thing but "more": "completely within the confines of"

Note that in does not actually say that something is not fully within the confines - it's just that while inside specifies this, in doesn't (and so can also be used in other situations, such as the window case mentioned above, where Annie isn't even partially in the window, except for in a visual sense).

  • 1
    I still feel the distinction in the bullet's case is a bit contrived. How about something like the following: The police recovered all the bullets from the crime scene, those inside the body and those that went through? In this example, "inside" is meant to contrast the location of the bullets.
    – Nico
    Commented May 28, 2014 at 18:04
  • @Nico Yes, there is a contrast there, but would the contrast not also be there if you used "in", on account of the contrasting structure of the sentence? Actually, I think a better example would be "He's got something in his eye" vs "He's got something inside his eye" - but I can't think of this type of example for bullets.
    – Alicja Z
    Commented May 28, 2014 at 18:13
  • Sorry, I didn't express myself clearly. In the bullet's case, I think most people will understand "inside the body" and "in the body" have the same meaning. Most people will use "in the body", because it's easier. If they have an additional reason to stress that the bullet is "within the confines of the body", then they may use "inside the body" instead.
    – Nico
    Commented May 28, 2014 at 18:15
  • @Nico Oh, I totally agree. "In" is easier and quicker, so generally if we don't need to make a point out of something being "within the confines", there's no reason not to use "in" instead of "inside". What about "He had a bullet in/inside his hand"? The "inside" version is non-painful only if his hand is in a fist, otherwise it implies that the bullet is embedded in his body...
    – Alicja Z
    Commented May 28, 2014 at 18:18
  • @Nico I think I'll clean up my comments here, this is getting long...
    – Alicja Z
    Commented May 28, 2014 at 18:19

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