Solfege is a synonym of solmization.

As nouns the difference between solmization and solfege

is that solmization is an alternative spelling of solmisation while solfège is a method of sight singing that uses the syllables do (originally ut), re, mi, fa, sol (or so), la, and si (or ti) to represent the seven principal pitches of the scale, most commonly the major scale. The fixed-do system uses do for C, and the moveable-do system uses do for whatever key the melody uses (thus B is do if the piece is in the key of B). The relative natural minor of a scale may be represented by beginning at la.