Conjunctions can be divided into two broad classes - coordinating and subordinating.

Coordinating conjunctions join pairs of clauses that are grammatically independent of each other.
Examples are: and, but, for, or, yet, so, nor, also, either…or, neither…nor etc.

• Birds fly and fish swim.
• I was annoyed still I kept quiet.
• Neither a borrower nor a lender be.
• There was little hope of success nevertheless they decided to perform the operation.

Words for repeated ideas can often be left out in the second of two coordinate clauses.

• She smokes and drinks. (= … and she drinks.)
• She is clever but careless. (… but she is careless.)