If is the basic word for a condition, but not the only one. Unless, as long as, provided, even if, in case and others give different meanings.
| Word | Meaning | Example |
|---|---|---|
| unless | if not | I'll go unless it rains. |
| as long as | only if | You can go out as long as you finish your homework. |
| provided / providing (that) | only if (more formal) | We'll start provided everyone is ready. |
| even if | it makes no difference | I'll go even if it rains. |
| in case | because it might happen | Take an umbrella in case it rains. |
| whether or not | it makes no difference | She'll come whether or not he does. |
Unless means "except if" or "if not". Use a present tense for the future. Use a comma when the unless clause comes first.
Do not use will or would in the unless clause. Use unless for an exception, not when something is known to be true.
These mean "only if". They set a condition. Provided and providing are more formal, and may be followed by that.
In case gives a reason for something you do now, because of what might happen. Compare it with if.
| if | in case |
|---|---|
| Take an umbrella if it rains.only when rain happens | Take an umbrella in case it rains.now, because it might rain |
For the usual precaution meaning, use a present tense after in case for the future.
These words start an imagined situation. The tense shows how likely it is.
| Likelihood | Tense | Example |
|---|---|---|
| Quite likely | present | Suppose it rains. What will we do? |
| Unlikely | past simple | Suppose it rained. What would we do? |
| Did not happen | past perfect | Suppose it had rained. What would we have done? |
✗I'll call you unless I will be late.
✓I'll call you unless I am late.
After unless, use a present tense for the future.
✗Take a coat in case it will be cold.
✓Take a coat in case it is cold.
For the usual precaution meaning, use a present tense after in case for the future.
✗As long as it will be sunny, we'll go.
✓As long as it is sunny, we'll go.
For an ordinary future condition, use a present tense after as long as.
See Zero and first conditionals: real conditions, The second conditional: unreal situations now or in the future, The third conditional: unreal past situations and Inverted conditionals: should you need, had I known, were it to.
Eight questions. Choose one answer for each.