CONDITIONALS

1. The first conditional
2. The second conditional
3. The third conditional

A conditional sentence is made up of two parts: an if-clause and a main clause. When the if-clause comes before the main clause, the two clauses are separated with a comma. When the main clause comes before the if-clause, then no comma is necessary.

EXAMPLE: If Tom arrives early, we'll have dinner together. (If-clause comes before main clause. Comma required.)
EXAMPLE: We'll have dinner together if Tom arrives early. (Main clause comes before the if-clause. No comma required.)

There are three main types of conditional. They are commonly referred to as the first, second and third conditionals (or the Type 1, Type 2 or Type 3 conditionals.)