Istiʿārah uses a word assigned to one meaning for another related meaning. Majāz is a broader category. Calling a brave man a “lion” is understandable through bravery, but legal expressions such as ownership, purchase, emancipation and divorce demand a closer analysis of legal effects.
Literal sense: the assigned or established meaning.
Transferred sense: the other meaning sought by a recognized relationship.
Connecting ground: the feature justifying that movement.
Not every verbal similarity licenses legal transfer. The jurist must identify the relation between the causes and the legal outcomes of the expressions concerned.