reflectivity vs echo

reflectivity and echo both are nouns.

Word	Noun	Adjective	Verb	Adverb
reflectivity	Yes	No	No	No
echo	Yes	No	Yes	No

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

reflectivity: the ability to reflect beams or rays
echo: the repetition of a sound resulting from reflection of the sound waves

Other hyponyms of reflectivity include replication, reverberation, sound reflection.

reflectivity (noun)	echo (noun)
the ability to reflect beams or rays	an imitation or repetition
the capability of quiet thought or contemplation	the repetition of a sound resulting from reflection of the sound waves
the fraction of radiant energy that is reflected from a surface	a reflected television or radio or radar beam
	a close parallel of a feeling, idea, style, etc.
	a reply that repeats what has just been said