There was a discussion in which I'd like you to help out. Suppose one is interested in a certain lady who happens to be in a relationship with someone else. Is it OK to try to 'displace' the other gentleman? After all the two aren't married, so technically she doesn't 'belong' to him.
Thank you for your anticipated response
Dating used to be clearer than it is today. It isn't unusual to see people treating a boyfriend / girlfriend relationship as if they are married. This has caused all sorts of complications.
Dating just means you are going places with a particular person. The rule used to be that you should date several people. It wasn't unusual for Sally to go on a date with Fred one day and the next week go out with Sam. When a person started dating one person most of the time, it was called going steady. But even while going steady, you might once in a while accept a date from someone else. When you were engaged, then you have made a commitment to one person, but it could be called off if things were not working out. Marriage was then for a lifetime.
The hard part of answering your question is that expectations have shifted. Technically in dating there is no displacing another person because there is no exclusiveness implied in dating. Today, people see it differently. From my point of view, simply ask if she would like to go out to dinner with you. If she says, "Yes," then wonderful. Have a fun evening. If it goes well, ask her another time.