add together vs summate

add together and summate both are verbs.

Word	Noun	Adjective	Verb	Adverb
add together	No	No	Yes	No
summate	No	No	Yes	No

As verbs, add together and summate are synonyms defined as:

Other synonyms of add together include add, add up, sum, sum up, tally, tot, tot up, total, tote up.

add together (verb)	summate (verb)
make an addition by combining numbers	determine the sum of
determine the sum of	form or constitute a cumulative effect