OK, I'm a total newbie, and I couldn't find any previous posts that address my problem...

I have an 83 240D with a manual transmission. The clutch appears to be functioning (i.e. it feels 'normal' when I depress it), but I can't get the car to engage in any gear. It wasn't as if this was a worsening issue - it just stopped working. It's not an emergency situation, as the car is sitting in my garage, but it obviously isn't driveable.

Based on this description, does anyone have a potential diagnosis, or can anyone provide suggestions for me to hone my search keywords?

Any help is appreciated!