a cardinal number, 1 plus 1.

a symbol for this number, as 2 or II.

a set of this many persons or things.

a playing card, die face, or half of a domino face with two pips.

amounting to two in number. ?

in two, into two separate parts

as halves

A bolt of lightning split the tree in two.

put two and two together

to draw a correct conclusion from the given circumstances; infer

It didn't require a great mind to put two and two together.

noun

brace , couplet , doublet , duet , duo , match , pair , twosome , yoke , bifurcation , bilaterality , binary , couple , deuce , dichotomy , diremption , dos , double , dual , duality , duplexity , duplicity , dyad , number , span , team , twain , twin , twins

adjective

amphibian , amphibious , bicameral , bifurcate , bigeminal , bilateral , binal , binary , bipartisan , bipartite , bisected , dichotomic , dichotomous , diploid , distichous , dual , dualistic , dyadic

verb

bifurcate , bisect , dichotomize , divide , halve