precedes a condition, must be followed by then which may optionally be followed by else.

   if (condition) then ''true_statement''
   else ''false_statement'';

   if boolean_condition then begin
      statement_one;
      statement_two;
   end
   else begin
      statement_three;
      statement_four;
   end;

Source: Reserved Words

See Also:

case, then, else.