Which type of fraction has a value less than one?

A proper fraction is defined as a fraction where the numerator (the top number) is less than the denominator (the bottom number). This characteristic ensures that proper fractions always have a value less than one. For example, in the fraction 3/4, the numerator 3 is less than the denominator 4, confirming that the value of this fraction is indeed less than one.

In contrast, an improper fraction has a numerator that is greater than or equal to the denominator, leading to values that are equal to or greater than one. Mixed numbers, which combine a whole number with a proper fraction, also have values that exceed one when considering the whole number portion. Whole numbers, by definition, are integers that take values of zero or greater, and thus they are not fractions at all, and certainly not less than one (except when it is zero).

The distinction of proper fractions makes them unique as values that are consistently below one, which is why this choice is the correct answer.