pediment vs gable wall

pediment and gable wall both are nouns.

Word	Noun	Adjective	Verb	Adverb
pediment	Yes	No	No	No
gable wall	Yes	No	No	No

As nouns, gable wall is a hypernym of pediment; that is, gable wall is a word with a broader meaning than pediment:

pediment: a triangular gable between a horizontal entablature and a sloping roof
gable wall: the vertical triangular wall between the sloping ends of gable roof

Other hypernyms of pediment include gable, gable end.

pediment (noun)	gable wall (noun)
a triangular gable between a horizontal entablature and a sloping roof	the vertical triangular wall between the sloping ends of gable roof