As well as if, there are a number of other words and phrases for expressing condition.
1. You can’t come in unless you have a ticket.
2. You can borrow the bike on condition that you return it by five o’clock.
3. In case of fire, dial 333. [usually seen on notices ; it means ‘when there is a fire’; don’t confuse with ‘take your mac in case it rains’; not it might rain.]
4. You can stay, as long as you don’t mind sleeping on the sofa, [less formal than so long as and less formal and not so strong as on condition that]
Providing (that) or provided (that) can also be used in examples 2 and 4. They are less formal and not so strong as on condition that but stronger and more restricting than as long as, e.g. Provided/Providing you don’t mind cats, you can stay with us. Note the use of supposing and what if (usually in spoken language) for possible situations in the future. What if is more direct, e.g. Supposing/What if he doesn’t turn up; what shall we do then?
Conditions with -ever :
However you do it, it will cost a lot of money.
You’ll get to the railway station, whichever bus you take.
Whoever wins the General Election, nothing will really change.
That box is so big it will be in the way wherever you leave it.
These four sentences can also be expressed using no matter.
No matter how you do it, it will cost a lot of money.
You’ll get to the railway station, no matter which bus you take.
Some nouns which express condition :
Certain conditions must be met before the Peace Talks can begin.
A good standard of English is a prerequisite for studying at a British University.
[absolutely necessary; very formal word]
What are the entry requirements for doing a diploma in Management at your college?
I would not move to London under any circumstances. It’s awful!
[ Notice in the examples in A and B how the present tense is used in the clause with the conditional word or phrase. Don’t say: Take your umbrella in case it will rain.]