add vs summate

add and summate both are verbs.

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

As verbs, add and summate are synonyms defined as:

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

add (verb)	summate (verb)
make an addition (to); join or combine or unite with others; increase the quality, quantity, size or scope of	determine the sum of
make an addition by combining numbers	form or constitute a cumulative effect
determine the sum of
state or say further
bestow a quality on
constitute an addition