1. One instance of some mathematical object contained with in another instance, e.g. a group which is a subgroup.

2. (domain theory) A complete partial order F in [X -> Y] is an embedding if

(1) For all x1, x2 in X, x1 F x1 <= F x2 and

(2) For all y in Y, x | f x <= y is directed.

("<=" is written in latex as \sqsubseteq).