riddle vs interpenetrate

riddle is a noun but interpenetrate is not a noun.

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

As verbs, riddle and interpenetrate are synonyms defined as:

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

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

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