The 'if' clause is a little bit different to the other clauses. We use 'if' when we are talking about cause and effect.
| If this happens... | → | ... that happens. |
The grammar for 'if' clause sentences is very similar to that of other future time clause sentences. The clause that comes with 'if' must be in the simple present. The other clause can use 'be going to,' 'will' or sometimes the present continuous.
The 'if' clause can come in the first or second part of the sentence. When the 'if' comes first, we can use the word 'then' to separate the two clauses, although we don't have to.
| First Clause | Second Clause |
| If you swim right after you eat, | then you'll get a stomachache. |
| If you take too long to get dressed, | you're going to miss your bus. |
| The cake is going to burn | if you leave it in the oven for any longer. |
| Shelly will come to the party | if you serve some peanut-free snacks. |
Notice that the part with the clause can come first or second. Remember, there must be a comma (,) if your time clause comes first!