summation vs congeries

summation and congeries both are nouns.

Word	Noun	Adjective	Verb	Adverb
summation	Yes	No	No	No
congeries	Yes	No	No	No

As nouns, congeries is a hyponym of summation; that is, congeries is a word with a more specific, narrower meaning than summation:

Other hyponyms of summation include aggregate, conglomeration.

summation (noun)	congeries (noun)
the arithmetic operation of summing; calculating the sum of two or more numbers	a sum total of many heterogenous things taken together
a concluding summary (as in presenting a case before a law court)
the final aggregate
(physiology) the process whereby multiple stimuli can produce a response (in a muscle or nerve or other part) that one stimulus alone does not produce