headache vs cephalalgia

headache and cephalalgia both are nouns.

Word	Noun	Adjective	Verb	Adverb
headache	Yes	No	No	No
cephalalgia	Yes	No	No	No

As nouns, headache and cephalalgia are synonyms defined as:

headache and cephalalgia: pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs

Other synonyms of headache include head ache.

headache (noun)	cephalalgia (noun)
something or someone that causes anxiety; a source of unhappiness	pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs
pain in the head caused by dilation of cerebral arteries or muscle contractions or a reaction to drugs