sinus sigmoideus vs sigmoid sinus

sinus sigmoideus and sigmoid sinus both are nouns.

Word	Noun	Adjective	Verb	Adverb
sinus sigmoideus	Yes	No	No	No
sigmoid sinus	Yes	No	No	No

As nouns, sinus sigmoideus and sigmoid sinus are synonyms defined as:

sinus sigmoideus and sigmoid sinus: an S-shaped dural sinus on the temporal and occipital bones

sinus sigmoideus (noun)	sigmoid sinus (noun)
an S-shaped dural sinus on the temporal and occipital bones	an S-shaped dural sinus on the temporal and occipital bones