construction vs understructure

construction and understructure both are nouns.

Word	Noun	Adjective	Verb	Adverb
construction	Yes	No	No	No
understructure	Yes	No	No	No

construction (noun)	understructure (noun)
the act of constructing something	lowest support of a structure
the commercial activity involved in repairing old structures or constructing new ones
drawing a figure satisfying certain conditions as part of solving a problem or proving a theorem
a thing constructed; a complex entity constructed of many parts
the creation of a construct; the process of combining ideas into a congruous object of thought
an interpretation of a text or action
a group of words that form a constituent of a sentence and are considered as a single unit