Study materials
Four sentences about tomorrow's meeting. All are grammatical, and each says something different about you.
I'll meet him tomorrow.
I'm going to meet him tomorrow.
I'm meeting him at ten tomorrow.
The train leaves at nine tomorrow.
The word tomorrow appears in all of them, yet the forms differ. So the form is chosen not by the time but by where the event came from: your decision, your plan, an arrangement, or a timetable.
Four forms, sorted by the origin of the event
Here is the whole system on one page. Read it from right to left: understand the situation first, then take the form.
| Where the event came from | Form |
|---|---|
| a decision made this second | will |
| a prediction you think | will |
| an intention formed earlier | be going to |
| a prediction from visible evidence | be going to |
| an arrangement with a time and a place | Present Continuous |
| an official timetable | Present Simple |
Will and be going to: when the decision appeared
These two are the easiest to confuse, because Ukrainian renders them identically. The difference is when the decision arose: just now or earlier.
We're out of milk. I'll buy some.
I'm going to buy milk after work.
The same split works for predictions. Will goes where you think so; be going to goes where the evidence is visible.
I think it will be cold tomorrow.
Look at those clouds. It's going to rain.
An arrangement and a timetable
Two present forms talk about the future, and they differ by their source. The Present Continuous is your own arrangement; the Present Simple is somebody else's schedule.
We're meeting the designer at ten.
The workshop starts at nine.
The check is simple: did you take part in the decision? If so, it is the Continuous. If a schedule set the time, it is the Simple.
No future after when
This habit costs the most mistakes. In a clause with when, as soon as, before, after or until, English uses a present tense even when tomorrow is meant.
I'll call you when I arrive.
We'll start as soon as everyone is here.
The logic is the same as in conditionals: the future is already carried by the main clause, so there is no need to say it twice.
The mistakes everyone makes
The first is putting will after when.
I'll call you when I will arrive. → I'll call you when I arrive.
The second is taking will where everything is long since arranged.
I'll meet the client at ten, it's in my calendar. → I'm meeting the client at ten.
The third is taking the Present Continuous for somebody else's timetable.
The train is leaving at nine every day. → The train leaves at nine every day.
All three are caught by one question. Who is the author of this event: me just now, me earlier, us together, or somebody else?
Try it right now
Describe your day tomorrow in English in four sentences, one for each form.
Then add a fifth beginning with when. Check that a present tense follows it.