Part of speech: Adjective
capable of being modified in form or character or strength (especially by making less extreme)
Example: the rhythm of physiological time is not modifiable except by interference with certain fundamental processes" - Alexis Carrel
The word "modifiable" comes from French modifiable.
modify – A related word in the same word family.
able – A related word in the same word family.
English has both Germanic and French words for the same things—'begin' vs 'commence', 'help' vs 'assist'.