NTS is cucking... A cuckold, at least here in America is a person who shares their partner with others and enjoys it. Whether there is humiliation or not, a person who willingly shares their partner for their own enjoyment is a cuckold. Ntr isn't cuckolding its just cheating and being unfaithful in general. Cuckoldry is a sexual fetish between 2 partners while, ntr is a person being stolen away without permission.
Before it became associated with the modern fetish, "cuckold" specifically meant a man whose wife was sexually unfaithful whether he knew or not; massive humiliation if/when he found out was default.
That's substantially different from...
- polygamy/polyamory by either sex
- orgies where all present more than consent to--are further aroused by--their romantic partner's full participation (i.e. "what I'm doing with these 2 women is even better
because I'm also watching my wife get DP'd by their husbands")
- a couple in a threesome ("of course my wife isn't mad... you were eating her pussy the whole time")
-
a fantasy setting where any or all of the above are socially normal
In the original/general sense, "cuckoldry"
is infidelity and humiliation over it. In the present sex-slang sense it's when the humiliation is fetishized, including as a way to cope when the infidelity is known and can't be stopped. ("Mystery NTR" being when
the stealth is fetishized for the audience and in-character for the cheater)
I don't see why "sharing"
without infidelity per se, or humiliation, should be considered part of that. Adjacent, sure. Similar enough to be "in a category with," but not "a type of."