When I run "who am i" at a UNIX prompt, what does "tty" and "ttys" stand for?

Question

I know this is a simple question, I'm just curious.

Answer 1

http://en.wikipedia.org/wiki/TTY

Answer 2

Teletype.

When Unix was first developed, built-in displays for computers were quite rare. I/O was accomplished by sending characters to another device. The teletype was the oldest and most established of these devices.

Answer 3

TeleTYpe (The S is "Serial").

Hint: Google is useful.