fleck vs nebula

fleck and nebula both are nouns.

Word	Noun	Adjective	Verb	Adverb
fleck	Yes	No	Yes	No
nebula	Yes	No	No	No

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

fleck (noun)	nebula (noun)
a small contrasting part of something	(pathology) a faint cloudy spot on the cornea
a small fragment of something broken off from the whole	an immense cloud of gas (mainly hydrogen) and dust in interstellar space
	cloudiness of the urine
	a medicinal liquid preparation intended for use in an atomizer

fleck (verb)	nebula (verb)
make a spot or mark onto