The French saying "to take a lover" is not the same as a boyfriend but more than a casual date
The word "paramour" or lover is implicitly French. When I was in London I heard many a French woman say that they would "take a lover" for the spring or summer because their life was too complicated for a relationship. On the surface it sounded like a hybrid between a steady date and friend for fun, but it was much more than that. A lover is not a secret nor is it not emotionally intimate. Rather, it's an extended passion and romance that can be emotionally fulfilling but you are still living single.
A pair of lovers are not a couple. They live separate lives and don't meet each others' friends or family. It can happen but it's not a must. Lovers are actually exclusive and not so much an open relationship but an extended form of a transitional one. What this means is that you are together for more than just romance but you are still available for the real thing. Basically, it's keeping yourself occupied while you date for the forever person with the "right now" one. A lover is never a significant other.
The duration of these relationships can vary. Sometimes its just a season. Other times it can be months or years. The one thing it is not is a lifetime. In Europe the term "taking a lover" is well understood. Here in North America it is not so clear unless you are in Quebec. Men mistake women who are interested in them as a lover for wanting them as boyfriends. Mais non! It's not so much tying a man down as it is having one for company as she looks for the real thing. Vive le difference!
Women respect a lover. She may even admire him. On some level there is friendship type love. He is a cross between a friend and a mistress (not sure what the male equivalent word is) but not a secret. He knows her life, her thoughts, plans and dreams, secret worries, wishes, and fears. It's a unique kind of soulmate. They are like the cat that keeps the seat warm for their owner. A lover keeps the heart open until the real love comes along. When a French woman takes a lover she is making a statement with that lifestyle choice to remain welcoming of true love.