I pretty much agree with the definitions already said (I only skimmed, in case there was a disagreement, I think Shai said it best, minus the rape). However, I'm really ok being in relationship as described as "boyfriends." However, I must express my contempt for the term "partner." It seems to be a term used exclusively for homosexuals, and it therefore implies that a homosexual relationship is distinctly different from a heterosexual one. Also, with SO, I'm ok with this term as a gender-neutral term for use in discussion of general terms, but I don't think I'll ever introduce someone as my SO.