We can express conditions with the help of such phrases as: as long as, only if, on condition that, provided that, providing that, etc. at the beginning of a subordinate clause.
You can play in the garden as long as you don’t ruin my roses.
I will accept your apology only if you apologize to the whole class.
He agreed to lend her money on condition that she returned it within a month.
Provided (that) and providing (that) are interchangeable when used as synonyms to “on condition that”, although provided (that) is more common.
You can drive a car abroad provided that you have an international license.
One can rent a flat provided one keeps it clean and doesn’t bother neighbors.
We’ll sign the contract providing all the points under discussion are included in it.
Unless is used instead of if…not in conditional sentences of all types.
You’ll gain weight unless you stop eating so much fast food.
He would be here by now unless he left the home so late and wasn’t stuck in a traffic jam.
Even if is used to talk about an imaginary situation to stress that something will happen no matter what.
Even if she loses her job, she’ll find a way to take care of her kids.
I will go to the studio next week to make the record even if I still have the flu.
We can use whether…or not to say that it’s not important if… or it doesn’t matter if.. something will happen or not.
Whether you like it or not, you are going to have to do the laundry first and then you can do whatever you want.
I want to check whether they have delivered the package or not.
In case (of) is used to talk about things we should do in order to be prepared for possible situations in the future.
Take some cash in case they don’t accept credit cards.
I took a pair of flip flops in case I rub a callus on my heel.
In case of emergency, call 122.