The words translated 'commensurable and agreeable to one another' (Greek) seem to be different ways of describing the same relation, with more or less precision.

They are equivalent to 'expressible in terms having the same relation to one another,' like the series 8, 12, 18, 27, each of which numbers is in the relation of (1 and 1/2) to the preceding.

The 'base,' or 'fundamental number, which has 1/3 added to it' (1 and 1/3) = 4/3 or a musical fourth.

(Greek) is a 'proportion' of numbers as of musical notes, applied either to the parts or factors of a single number or to the relation of one number to another.

The first harmony is a 'square' number (Greek); the second harmony is an 'oblong' number (Greek), i.e.a number representing a figure of which the opposite sides only are equal.