What constitutes a housewife?

I am mildly embarrassed to admit I enjoy watching Bravo's Real Housewives series. I admit I am probably dumber for watching it and have been watching it secretly for seasons. But I need to know, as I am watching The Real Housewives of New York, what constitutes a housewife? I thought it was someone who has kids, a family, something along those lines. I see there are two woman on this show who are not married or divorced without kids, how is that a housewife, I thought that was just being single and living life?? Even the woman on the show who are divorced with kids the show does not depict the women doing housewife things like helping your kids with homework, juggling plans with kids and play dates with work and life and even charity events?

Someone please explain this to me, please!