In mathematics, a rational number is any number that can be expressed as the quotient or fraction p/q of two integers, a numerator p and a non-zero denominator q.[1] Since q may be equal to 1, every integer is a rational number. The set of all rational numbers, often referred to as "the rationals", is usually denoted by a boldface Q (or blackboard bold Q {displaystyle mathbb {Q} } mathbb {Q} , Unicode ℚ);[2] it was thus denoted in 1895 by Giuseppe Peano after quoziente, Italian for "quotient".