Hyphens are usually used to connect numbers and words in modifying phrases. Such is the case when used to describe dimensional measurements of weight, size, and time, under the rationale that, like other compound modifiers, they take hyphens in attributive position (before the modified noun), although not in predicative position (after the modified noun). This is applied whether numerals or words are used for the numbers. Thus " woman" and " woman" or " wingspan" and " wingspan", but "the woman is 28 years old" and "a wingspan of 32 feet". However, with symbols for SI units (such as "m" or "kg")—as opposed to the "names" of these units (such as "metre" or "kilogram")—the numerical value is always separated from it with a space: "a 25 kg sphere". When the unit names are spelled out, this recommendation does not apply: "a sphere", "a roll of film".