Partially Complete

I don’t know what it is about the designation “Semi Permanent”… That just screams out ILLOGICAL to my inner-Vulcan brain. Isn’t semi-permanent kind of like being partially complete? I mean either it IS or it ISN’T, right? Is this a half-full or half-empty kind of thing? (After researching it a bit, I’ve learned that there are many types of makeups and hair colors and beauty styles which are referred to as semi-permanent. So I say to all of my male friends: “Who knew?”)

Anyway. It just seemed an odd phrase to me. Maybe I am the only confused one…