What is a good mnemonic rule that an English learner can use to remember the difference between its (possessive adjective: a team has started its lunch) and it's (verb: it's raining)?
I'm not sure of how good a mnemonic this is, but it's always worked for me. When proofreading, I simply remind myself:
You can't remove an apostrophe when it's taking the place of a letter.
So, when I say:
It's supposed to rain tomorrow.
I recognize that "It's" means "It is", so I leave the apostrophe in. But when I type and proofread:
The house is losing it's foundation. [sic]
I realize that "it's" does not mean "it is"; it means "the foundation belonging to it", so I remove the apostrophe:
The house is losing its foundation.
If you don't like my method, it's easy to find lots more on the subject.
You just know that it's stands for it is, two words.
Its is just a single word, like my, your or his.
When reading, you just see if it is a single word or two words "linked" with an apostrophe.
For writing, you may employ this mnemonic:
I'm crying and saying, "it's not my fault!"
A tear will resemble to write it with an apostrophe.
This is a new answer (Jan 2015) to a two-year old question (Jan 2013).
I revived this thread because I believe this provides a best-of-class answer that complements the well-deserved selected answer by J.R.. It's a tall order to come in so late with such a bold statement. I only ask that as you assess the value of this answer (for better or worse!), to keep in mind that this is relatively new, and so this has not received the same benefit of attention as answers given two years ago when the question was first asked.
Until now, there has been no gold standard, easy-to-remember mnemonic that helps someone generate the correct form-to-meaning of its vs. it's. So I created a mnemonic device specifically for this answer. It's short, clear, and easy-to-remember.
This is the mnemonic device:
That's it! That's the mnemonic device:
It's. If you can remember that, then you can remember what it means. Don't believe me? Just watch.
Question: What is that thing I just told you to remember? What is it, if you break it into its parts?
Answer: It's a pronoun followed by apostrophe S.
Just look at it (below). Doesn't that look like a pronoun? Followed by apostrophe S? Is that so hard?
it 's pronoun apostrophe S It's a pronoun followed by apostrophe S.
Let's do that again.
It's <-- What is that thing to the left? It's a pronoun followed by apostrophe S.
Put it all together!
- What is that?
It's a pronoun followed by apostrophe S.
a pronoun followed by apostrophe S.
It'smeans "It is".
itsis the possessive pronoun.
Explain it please!
it's cues the recall of "the sentence" (#3 above) describing what
it's is. You know you have to write that sentence with the apostrophe. And that sentence demands the "it is" interpretation! Now you know
it's means "it is" and conversely,
its must be the possessive form.
This mnemonic should be spread to the four corners of the English speaking world!
(And, of course, credit given to CoolHandLouis. :)
Its and my is "just one word".
"A team has started its lunch."
If I can substitute its (one word) with another possessive adjective my (one word), and the resulting phrase is grammatical then there is no need for the apostrophe e.g.,
A team has started my lunch
"my lunch" is grammatical so no apostrophe is required (the possessive adjective, its, is 'just one word'.)
"Today it's raining"
When we substitute it's raining (or its) with my we get:
Today my raining.
"My raining" as a phrase is not grammatical so it's is the correct spelling (two words; it + is)
Today it is raining = it's raining.
Further examples: (thinking 'yes' or 'no' for grammatical and ungrammatical)
The company has lost __ licence.
The company has lost my licence ----> grammatical ---> my ('just one word') ---> its
Check to see if __ gone
Check to see if my gone ----> ungrammatical ---> we need two words ---> it's (it + has)
The reef shark chases __ prey through the coral
... chases my prey through the coral ----> grammatical ---> my ('just one word') ---> its
This isn't my book, __ Fernando's.
This isn't my book, my Fernando's. ----> ungrammatical ---> we need two words ---> It's (It + is)
The dog is eating __ dinner.
The dog is eating my dinner ----> grammatical ---> my ('just one word') ---> its
Another not-quite-mnemonic method of remembering. This may not be helpful to people who have no exposure to English poetic forms:
I learned to keep them straight by keeping in mind the poetic form, 'tis.
It's is ..... the same as 'tis.
'Tis the season to be jolly
....Whether 'tis nobler in the mind to suffer the slings and arrows of outrageous fortune
'Tis but a scratch
These all mean the same as it's. Conveniently, they are written with the same four characters, rearranged - move the apostrophe and the t to the front, and you go from it's to 'tis.
The possessive its is not a synonym for 'tis, so it cannot be rearranged in the same way, so it doesn't have an apostrophe.
So the "mnemonic" is again:
It's is ..... the same as 'tis.
Emphasize the bold parts to give it a lilting rythm.