I found many candidates in ReVo: alnomo, alinomo, kaŝnomo, kromnomo, karesnomo. I doubt they are all synonyms. In which situations should I use each one?
I'd like to find the one to use when presenting oneself. For example "Hi, my name is Robert, but my nickname is Bob". Or when someone has a really long name, I might want to ask "Do you have a nickname"?
Kromnomo - nickname
Kaŝnomo - alias, pen name; a fake name to hide your real name
Karesnomo - a familiar name (for friends only)
So, if you're asking someone with a long or difficult name if you can call them something else, it would be kromnomo -- unless you want to call him "honey" or "Billy Buttons."
In addition to Tomaso Alexander's excellent answer, I would like to remark that alinome is the most popular translation of English aka, e.g. “Miguel Gutiérrez Adúriz, alinome Liven Dek”. It gets ~96000 google hits, while kromnome gets ~900. OTOH, the nouns alinomo and kromnomo get similar google hit numbers, and in the particular case of an author's pen name, plumnomo is the most popular choice, even if the other alternatives are possible and actually used.
Related words:
Moknomo - sobriquet (referring to ridiculous nature, unflattering, teasing, mocking) nickname
Pseŭdonimo - Kaŝnomo de verkisto aŭ artisto
Alnomo - alias, nickname
