An inability to recognize faces of familiar people; "face blindness".
This can be due to brain damage or it can be congenital.
There are different forms and levels; some people may have difficulty recognizing family members.
I always assumed I was just bad at faces due to lack of practice or something, but now I'm beginning to wonder if I have some form of mild prosopagnosia. I've worked in the same building for 15 years; it took over a decade to firmly establish some people's faces in my memory. Mom was the opposite: she had this near-magical ability to recall the name and social/familial context of someone she'd met only once twenty years back.
Etymology: 1950s, from Greek prosopon, face and agnosia, not knowing
