Yes, 1/2 is a rational number. A rational number is any number that can be expressed as the quotient or fraction p/q of two integers, where p is the numerator and q is the denominator, and q is not equal to zero.
In the case of 1/2, the numerator p is 1 and the denominator q is 2. Since both 1 and 2 are integers and the denominator is not zero, 1/2 fits the definition of a rational number.
Rational numbers include all integers, fractions, and terminating or repeating decimals. Since 1/2 is a fraction of two integers, it is clearly a rational number.