What are shortened forms of first names called?

Factual Questions
1

E.g. “Sam” for “Samuel” or “Samantha”
“Mike” for “Michael”

The only guess my co-workers have come up with is “nicknames,” but most of us associate that with “skippy,” “Duke” and the like.

So, is “Sam” a nickname? If not, what is it?

Sua

2

Nickname is acceptable, although that’s a broader term, as you note. I think the word you’re looking for is “diminutive.” (Yes – it’s a noun AND an adjective! ;))

–Cliffy <-- nickname

3

Dictionary dot com seems to think it’s a nickname. Sounds right to me.

Incidentally, my real username isn’t actually “pravnik”; pravnik is just short for “Obi-Wan”.

4

Except that that usually referrs to the form of the name with y on the end (in English, at least: Other languages have their own ways of forming diminutives). So, for instance, the diminutives for “Samuel” and “Michael” would be “Sammy” and “Mikey”.

5

I have an old Reader’s Digest Great Encyclopedic Dictionary with a dictionary of first names in the back, and it lists forms like “Mike” and “Sam” as “diminutives” under the entries for Michael and Samuel. (Actually it refers to them as “Dims.”, but I’m extrapolating a little here.)