Provided(that) can replace  If when there is a strong idea of limitation or restriction.

You can camp here if you leave no mess.

We can also say:

You can camp here provided you leave no mess.

You can use this room if you leave no mess.

We can also say:

You can use this room provided you leave no mess.

You can come to my house if you would like to talk to my father.

We can also say:

You can come to my house provided you would like to talk to my father.

She can take her vacation if she has finished her duty.

We can also say:

She can take her vacation provided she has finished her duty.

Otherwise = if this hadn’t happened

She used her calculator; otherwise she would have been longer.

We can also say:

If she hadn’t used her calculator she would have been longer.

I took an English Course; otherwise I would have been bad in English subject.

We can also say:

If I hadn’t taken an English Course I would have been bad in English subject.

He bought a new house; otherwise he could have lend you some money.

We can also say:

If he hadn’t bought a new house he could have lend you some money.

Otherwise =  if this didn’t happen

His father pays his fees; otherwise he wouldn’t be here.

We can also say:

If his father didn’t pay his fees he wouldn’t be here.

I come on time; otherwise I couldn’t take my English test.

We can also say:

If I didn’t come on time I couldn’t take my English test.

She pays her fees; otherwise she couldn’t take the final test.

We can also say:

If she didn’t pay her fees she couldn’t take the final test.

Otherwise = ‘ if it doesn’t happen

You must be back before midnight; otherwise you will be locked out.

We can also say:

If you are not back by midnight you’ll be locked out.

We must leave before five; otherwise we’ll be late for the concert.

We can also say:

If we don’t leave before five we’ll be late for the concert.

John must go early in the morning; otherwise he’ll miss the train.

We can also say:

If John doesn’t go early in the morning he’ll miss the train.

but for = if it were not for/if it hadn’t been for

My car broke down.But for that we would have been in time.

We can also say:

My car broke down. If it had not been for that we would have been in time.

My father pays my fees. But for that I wouldn’t be here.

We can also say:

My father pays my fees. If it were not for that I wouldn’t be here.

I had a flat tire. But for that I would have been on time.

We can also say:

I had a flat tire. If it had not been for that I would have been on time.

My sister broke her car. But for that she would have been in time.

We can also say:

My sister broke her car. If it had not been for that she would have been in time.

Unless + affirmative verb = if + negative

Unless you start at once you will be late.

We can also say:

If you don’t start at once you will be late.

Unless you study hard you won’t pass the exam.

We can also say:

If you don’t study hard you won’t pass the exam.

Unless you take an English course you will have bad English.

We can also say:

If you don’t take an English course you will have bad English.

Unless you had a permit you couldn’t get a job.

We can also say:

If you didn’t have a permit you couldn’t get a job.

Whether…or

You must go tomorrow whether you are ready or not.

I must go tomorrow whether I am ready or not.

We must go tomorrow whether we are ready or not.

John must go tomorrow whether he is ready or not.

He must go tomorrow whether he is ready or not.

Mary must go tomorrow whether she is ready or not.

They must go tomorrow whether they are ready or not.

Even if = even though

You must take an English lesson even if you don’t like it.

We can also say:

You must take an English lesson even though you don’t like it.

You must go by plane even if you don’t like it.

We can also say:

You must go by plane even though you don’t like it.

Mary has to go by ship even if she doesn’t like it.

We can also say:

Mary has to go by ship even though she doesn’t like it.

John must take an English course even if he doesn’t like it.

We can also say:

John must take an English course even though he doesn’t like it.

Want, wish, would like/care:

If you want to come I’ll get a ticket for you.

we can also say:

If you wish to come I’ll get a ticket for you.

We can also say in more polite sentence:

If you would like to come I’ll get a ticket for you.

If you want to see the photographs I’ll bring them round.

we can also say:

If you wish to see the photographs I’ll bring them round.

We can also say in more polite sentence:

If you would care to see the photographs I’ll bring them round.

If she wants to leave her car here she can.

We can also say:

If she wishes to leave her car here she can.

We can also say in more polite sentence:

If she would like to leave her car here she can.

If , even if

Compare:

You must go tomorrow if you are ready.

You must go tomorrow even if you aren’t ready.

Compare:

John must go tomorrow if he is ready.

John must go tomorrow even if he isn’t ready.

Compare:

He must go tomorrow if he is ready.

He must go tomorrow even if he isn’t ready.

Compare:

Mary must go tomorrow if she is ready.

Mary must go tomorrow even if she isn’t ready.

Compare:

She must go tomorrow if she is ready.

She must go tomorrow even if she isn’t ready.

Compare:

We must go tomorrow if we are ready.

We must go tomorrow even if we aren’t ready.

Compare:

They must go tomorrow if they are ready.

They must go tomorrow even if they aren’t ready.