a, Are you a student?
If so, the ticket is half-price.
If not, the ticket is full price.
b,It`s a popular concert. Do you have a ticket?
If so, you`re lucky.
If not,you`re out of luck.
2, adverb clauses of condition: Using whether or not and even if
a, I`m going to go swimming tomorrow whether or not it is cold.
b, I have decided to go swimming tomorrow. Even if the weather is cold, I`m going to go swimming.
---whether or not, even if -give the idea that a particular condition does not matter. The result will not change.
3,adverb clauses of condition: using in case
a, I`ll be at my uncle`s house in case you (should) need to reach me.
---in case expresses the idea that something probably won`t happen, but it might. In case means "if by chance this should happen."
note: Using should in an adverb clause emphasizes the speaker`s uncertainty that something will happen.
4, adverb clauses of condition: Using unless
a, I`ll go swimming tomorrow unless it`s cold.
b, I`ll go swimming tomorrow if it isn`t cold.