I go to the gym three days a week at the same time.  I see many of the same people each time, but I have never talked to them.  I know their patterns.  I was aware that one woman I saw each time was not there for a long time.  When she returned, I was walking past her and I mentioned that I had not seen her for a long time.  She said she had foot surgery and was gone for three months.  For a few days, we smiled and said hello.  As I was leaving one day, she asked me my name and introduced me to another man she was talking to.

I now know the names of two people I have seen for almost two years.