teras vs foetus

teras and foetus both are nouns.

Word	Noun	Adjective	Verb	Adverb
teras	Yes	No	No	No
foetus	Yes	No	No	No

As nouns, foetus is a hypernym of teras; that is, foetus is a word with a broader meaning than teras:

teras: (medicine) a grossly malformed and usually nonviable fetus
foetus: an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal

Other hypernyms of teras include fetus.

teras (noun)	foetus (noun)
(medicine) a grossly malformed and usually nonviable fetus	an unborn or unhatched vertebrate in the later stages of development showing the main recognizable features of the mature animal