continuance vs longueur

continuance and longueur both are nouns.

Word	Noun	Adjective	Verb	Adverb
continuance	Yes	No	No	No
longueur	Yes	No	No	No

As nouns, longueur is a hyponym of continuance; that is, longueur is a word with a more specific, narrower meaning than continuance:

continuance: the period of time during which something continues
longueur: a period of dullness or boredom (especially in a work of literature or performing art)

Other hyponyms of continuance include clocking, residence time, span, stint, stretch, time scale, note value, time value, value, rule.

continuance (noun)	longueur (noun)
the act of continuing an activity without interruption	a period of dullness or boredom (especially in a work of literature or performing art)
the property of enduring or continuing in time
the period of time during which something continues