length vs continuation

length and continuation both are nouns.

Word	Noun	Adjective	Verb	Adverb
length	Yes	No	No	No
continuation	Yes	No	No	No

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

length (noun)	continuation (noun)
a section of something that is long and narrow	the act of continuing an activity without interruption
the linear extent in space from one end to the other; the longest dimension of something that is fixed in place	the consequence of being lengthened in duration
continuance in time	a Gestalt principle of organization holding that there is an innate tendency to perceive a line as continuing its established direction
the property of being the extent of something from beginning to end	a part added to a book or play that continues and extends it
size of the gap between two places