From Teflpedia

–ment is an English noun suffix. It is generally added to verbs to nominalise them, e.g. move --> movement.

Words ending -dge may drop the E before -ment, e.g. judge --> judgment; but they also may not, e.g. judge --> judgement.

These words are stressed in the standard way, which means the e is usually reduced to a schwa sound.

Note that in French, -ment is an adverb suffix, equivalent to English -ly.