brain-stem vs brainstem

brain-stem and brainstem both are nouns.

Word	Noun	Adjective	Verb	Adverb
brain-stem	Yes	No	No	No
brainstem	Yes	No	No	No

As nouns, brain-stem and brainstem are synonyms defined as:

brain-stem and brainstem: the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus

Other synonyms of brain-stem include brain stem.

brain-stem (noun)	brainstem (noun)
the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus	the part of the brain continuous with the spinal cord and comprising the medulla oblongata and pons and midbrain and parts of the hypothalamus