marriage: 1) the state of being married, 2) a wedding 3) of married 3) a close union.
religiously, marriage has been often, but not always, been defined as mike states: but that is a religious definition, not a legal one. and we are talking about legalities under the law, not what an individual church (or its ardent parishoners) desires.
the constitution of the united states makes no such territorial claim. moreover, it significantly questions the ability of any one religion to define any issue over the objections of another.
therefore, if even one church (and there are many more than one church), which is recognized as an actual religious organization/institution, views any issue in a significantly differing manner, the law, constitutionally, is supposed to reflect that diversity.
considering the sorry state of actually teaching the basics of the bible that, imho, most churchs practise...there should, in the 21st century, be no significant reason why individual churches, who wish to interpret the bible in their own way, should be legally barred from doing so.
moreover: if the state, a (supposedly - constitutionally) irreligious institution, engages in any activities, even marriage, they should remain neutral and impartial.
i don't think any one is trying to steal the word 'marriage': sorry that your view on 'marriage' as an intitution is so weak.
i, on the other hand, am quite significantly secure in my heterosexuality, the state of my marriage, and comfortable with the teachings of my faith, that allowing two legally consenting adults the priviledge of doing with thier own lives what they wish without my ( or my taxpayer funded state) intereference: to define thier own existence, so they may engage in lawful legal contracts that should be recognized BY THE STATE, is going to do me absolutely no harm whatsoever.
trying to redefine the argument with that lame ' a box is a box' shite is about a lame as the once used ' a black can't marry a white' argument : it is all backwards thinking...no, i take that back: it is NOT thinking; it's parroting the company line..there are other, taxpaying, honest, hard-working, patriotic citizens of both (all) our countries that that sort of excuse making should be beyond even bringing up...
next thing you know, someone'll start with the : 'whats next..do you sanctify a marriage between a man and a goat ?' line...aside from being pure bollux, i'm sure there's more than a few farmers in montana that's quarrel with that one...
you either believe in getting the 'state' out of our lives, or you believe in 'state' control of our lives: this is a defining issue.
lift up your head...and remember what your life is !