covering vs theca

covering and theca both are nouns.

Word	Noun	Adjective	Verb	Adverb
covering	Yes	No	No	No
theca	Yes	No	No	No

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

covering (noun)	theca (noun)
the act of protecting something by covering it	outer sheath of the pupa of certain insects
the work of applying something	a case or sheath especially a pollen sac or moss capsule
the act of concealing the existence of something by obstructing the view of it
an artifact that covers something else (usually to protect or shelter or conceal it)
a natural object that covers or envelops