riddle vs sieve

riddle and sieve both are nouns.

Word	Noun	Adjective	Verb	Adverb
riddle	Yes	No	Yes	No
sieve	Yes	No	Yes	No

As nouns, sieve is a hypernym of riddle; that is, sieve is a word with a broader meaning than riddle:

riddle: a coarse sieve (as for gravel)
sieve: a strainer for separating lumps from powdered material or grading particles

Other hypernyms of riddle include screen.

As verbs, sieve is a hypernym of riddle; that is, sieve is a word with a broader meaning than riddle:

riddle: separate with a riddle, as grain from chaff
sieve: separate by passing through a sieve or other straining device to separate out coarser elements

Other hypernyms of riddle include sift, strain.

riddle (noun)	sieve (noun)
a coarse sieve (as for gravel)	a strainer for separating lumps from powdered material or grading particles
a difficult problem

riddle (verb)	sieve (verb)
explain a riddle	distinguish and separate out
set a difficult problem or riddle	separate by passing through a sieve or other straining device to separate out coarser elements
speak in riddles	check and sort carefully
pierce with many holes	examine in order to test suitability
separate with a riddle, as grain from chaff
spread or diffuse through