interval vs clearance

interval and clearance both are nouns.

Word	Noun	Adjective	Verb	Adverb
interval	Yes	No	No	No
clearance	Yes	No	No	No

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

interval: the distance between things
clearance: the distance by which one thing clears another; the space between them

interval (noun)	clearance (noun)
the distance between things	permission to proceed
a set containing all points (or all real numbers) between two given endpoints	the distance by which one thing clears another; the space between them
the difference in pitch between two notes	vertical space available to allow easy passage under something
a definite length of time marked off by two instants