Mar 10:8 And they twain shall be one flesh: so then they are no more twain, but one flesh.
Alternative: And they shall be two in one body so that they are no longer two but one in the physical nature of things.
The version of this verse in Mat. 19:5 is examined here. The play on words here is in the word for meat, which means not only meat in the sense of the body, but in Greek meat in the sense of the physical nature of reality. It was used to denote what was really tangible, what we can get a hold on. We have a similar idea in modern English when we talk about "the meat of an argument" but in Greek the idea was less about the "core" of things and more about what is physical, what we can hold on to. In English, we might say that someone embodies a certain charactertistic by saying, for example, "He is Greed in the flesh." This is very close to the way this word is used in Greed.
Our temporal world exists for the purpose of transformation but that transformation is hard to pin down on a theoretical levels, but in the sexes we see transformation in the flesh. Though our two forms of humanity have separate charactertistics and souls, we are designed as pieces that fit together in one complete unit. Our different parts fit together in the physical nature of things and become productive: creating new life, new flesh.
For Christ, marriage wasn't just about love or the sex act. Like so much of his work, it is about what is productive, what is beautiful as opposed to worthless (the two words in Greek that we mistranslate as good and evil). Love and sex only become physically productive when the two sexes are united and with that union comes the responsibilities of acting as one unit, a single team, where our partners survival is necessary for that of our own and the family and life that we have produced together.
To say that one sex or the other is more important or better is just as silly as saying that the jacket or pants are more important in creating a suit or that the handle or bowl are more important in a spoon. It is their two parts together that make them complete, that make it a marriage, a suit, or a spoon. Take away either and it doesn't work as it should. The separate parts may have uses in themselves, but they are not what they were physically meant to be.
"They shall be" is from eimi (eimi), which means "to be," "to exist," "to be the case," and "is possible." (The form used here is the future form esomai.)
"Twain" is from duo (dyo), which means "two."
Not translated is eis (eis), which means "into (of place)," "up to (of time)," "until (of time)," "as much as (of measure or limit)," "as far as (of measure or limit)," "towards (to express relation)," "in regard to (to express relation)," "of an end or limt," and "for (of purpose or object)."
"One" is from heis (heis), which means "one," "single," and "one and the same." This adjective is irregular, having a number of forms depending on sex, number, and case: heis, henos, heni, hen, hena, mia, mias, miai, mian; hen, henos, hen. The form here is mia, feminine singular.
"Flesh" is sarx (sarx), which means "flesh," "the body," "fleshy," "the pulp of fruit," "meat," and "the physical and natural order of things" (opposite of the spiritual or supernatural).
"No more" is from ouketi (ouketi), which means "no more," "no longer," "no further" and generally, "not now."
"But" is from alla (alla), which means "otherwise," "but," "still," "at least," "except," "yet," nevertheless," "rather," "moreover," and "nay." It denotes an exception or a simple opposition.