In music, the terms additive and divisive are used to distinguish two types of both rhythm and meter:

• A divisive (or, alternately, multiplicative) rhythm is a rhythm in which a larger period of time is divided into smaller rhythmic units or, conversely, some integer unit is regularly multiplied into larger, equal units.

• This can be contrasted with additive rhythm, in which larger periods of time are constructed by concatenating (joining end to end) a series of units into larger units of unequal length, such as a ⁵
  ₈ meter produced by the regular alternation of ²
  ₈ and ³
  ₈ (London 2001, §I.8).

When applied to meters, the terms perfect and imperfect are sometimes used as the equivalents of divisive and additive, respectively (Read 1969, 150).

For example, 4 may be evenly divided by 2 or reached by adding 2 + 2. In contrast, 5 is only evenly divisible by 5 and 1 and may be reached by adding 2 or 3. Thus, ⁴
₈ (or, more commonly, ²
₄) is divisive while ⁵
₈ is additive.

Source: Additive rhythm and divisive rhythm – Wikipedia