riddle vs permeate

riddle is a noun but permeate is not a noun.

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

As verbs, riddle and permeate are synonyms defined as:

Other synonyms of riddle include diffuse, imbue, interpenetrate, penetrate, pervade.

riddle (noun)	permeate (noun)
a coarse sieve (as for gravel)
a difficult problem

riddle (verb)	permeate (verb)
explain a riddle	pass through
set a difficult problem or riddle	spread or diffuse through
speak in riddles	penetrate mutually or be interlocked
pierce with many holes
separate with a riddle, as grain from chaff
spread or diffuse through