This cracks me up, because this is exactly the one that gets to me the most, except it's the number of people playing bass guitars who want to insist that it's just some weird thing called a "bass," as though a "bass" can exist outside of an instrument category. It can't, unless you're talking about a fish.
You have bass saxophones, you have bass viols, you have bass clarinets, and we play bass guitars.
The fact that many people, including the person who sold you your first one, didn't bother to include the obvious instrument category in the name when you first heard it does not mean your instrument doesn't fall into that category. It is not in a category of its own named only for its playing register. No soprano sax player ever went around yelling at people that his instrument is just "a soprano."
I blame the poor state of music education for this mess, since once-upon-a-time our grade school music classes taught us about different kinds of instruments and the various registers they played in, but it's increasingly exacerbated by people who insist on clinging to this error even though it's been pointed out to them.
Bass guitar
Now, get off my lawn.
Bass guitar is the most played instrument to play bass, so it's a bass.
You can throw double bass in by the way.
Also guitar is not refered to with it's range, so by opposition bass guitar is called only with it's range.
That's the natural order of things in the universe.
