I've always thought that when using a type 1 conditional, we should always use "will/won't be able to" instead of "can/can't", but then I come up with some contexts where "can/can't" seems to be fine too. I don't know why. Can somebody explain?

Context 1

A: The bus station will be closed by 19:00. Will you need a ride?

B: It's okay. There's another station down the street. If it stays open, I can still take a bus tomorrow.

Context 2

A: I really want to repair our roof, but it will cost about 3,000 dollars.

B: I have already applied for the compensation, but the approval process is going to take at least 30 days. If we receive more than 3,000 dollars, we can use the money to repair the roof next month.

Context 3

A: Do you know where to buy some apples?

B: Why?

A: They have some of the best apples in the world here, and we are leaving early tomorrow morning. If I don't buy some tonight, I can't make some delicious apple juice for my parent tomorrow.

PS: I think maybe contexts 1 and 2 are more suitable for "can", while context 3 is a little disputable. If someone can explain this, I will really appreciate it.

  • A lot of more complex so-called tenses in English, native speakers often don't use when the temporal relationships are clear without. There is no "future tense" in English - the simple present, the modal "will" and the complex "be going to" are all ways in which we sometimes express future meaning.
    – Colin Fine
    Commented Oct 25, 2023 at 18:59

3 Answers 3


"I can't make some delicious apple juice":-

This is a direct sentence suggesting a straightforward consequence by implying limitation in your ability to do that thing(to make some delicious apple juice) if you don't do the 1st thing(buying of some delicious apples).

"I will not be able to make some delicious apple juice"-

This is a bit more formal sentence highlighting the future consequence by implying explicitly the inability to that thing (to make some delicious apple juice)suggesting a sense of planning.

  • That's quite a good explanation. I will say that the first one implies the lack of opportunity while the other is the lack of ability. What do you think about the "can" examples in context 1&2?
    – Skywarrior
    Commented Oct 24, 2023 at 8:39

I think that, in (1) and (2), the speaker is imagining themself in the hypothetical situation and therefore thinking of the possibility in the present tense.

"The bus station is still open, so I can take a bus." (Why would there be two bus stations in the same street?)

"We have received more than $3000, so we can repair the roof."

(3) is a negative sentence, so I don't find can't so natural.

"If I don't buy apples tonight, I won't be able to make any apple juice tomorrow."

  • For some reason, "can't" seems to be less acceptable in future tense.
    – Skywarrior
    Commented Oct 24, 2023 at 9:18
  • 1
    Acceptable to whom? You were told in response to your original question on ELU that 'can't' is often used when speaking about the near future. Commented Oct 24, 2023 at 10:25
  • That’s not the point. The point is that the negative form is less acceptable than “can” when referring to the future.
    – Skywarrior
    Commented Oct 24, 2023 at 10:59
  • @Skywarrior - it is equally 'acceptable'. Kate is right. If you crash your car today, you can't drive it to the beach tomorrow. If you marry Jane today, you can't date Mary next week. Commented Oct 24, 2023 at 11:01
  • 1
    It's true that I said that I found 'won't be able to' more idiomatic in your 'apple juice' example. If you don’t ask him nicely, you can’t get any useful information from him describes a general truth, but if you add tomorrow to make it a prediction, I think won't be able to sounds better - but there isn't a hard and fast rule. Commented Oct 24, 2023 at 12:05

First, this isn't particular to first conditionals -- this is just about "can".

One function of "can" is to indicate the ability to do something in the future. It also strongly implies that that's what will happen.

Your first two sentences can be rewritten like this:

If it stays open, I will have the ability to take a bus tomorrow (so that will be my plan).

If we receive more than 3,000 dollars, we will have the ability to use the money to repair the roof next month (and we should do that).

Your third sentence isn't correct though. This function of "can" always indicates an ability. Even if you negate the phrase, you don't negate the ability, you only negate the action itself, indicating the ability to not do something. It cannot indicate the inability to do something.

So if we take your third sentence, and use "can" and "not" instead of "can't", we get this:

If I don't buy some tonight, I can [not make some delicious apple juice for my parent] tomorrow.

This means "I will have the ability to not make apple juice", which means "not making apple juice" is an option, but I could also choose to make it.

  • can and am able. can and will be able. I will be able to take the bus.
    – Lambie
    Commented Oct 25, 2023 at 18:58

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