Polyamory is differentiable from some other forms of nonmonogamy (including adultery) in that it is future-oriented. Poly relationships are not located solely in the moment, but have intentions (though perhaps tacit and vaguely defined) of at least adding to a base of experience possibly so far as signifying a life-long and emotionally attached commitment.
Anthony D. Ravenscroft, Polyamory: Roadmaps for the Clueless and Hopeful: An Introduction on Polyamory
adultery, polyamory, relationships