"Who is the technician?"

Translation: Pwy ydy'r technegydd?

[frannyglass79]

Could I also say "pwy sy'n y technegydd?"

[ibisc]

No. If you asking who in particular has a particular job or function or name, then it must be ydy. If you are asking who in general is a whatever, then it is sy:

• *Pwy ydy'r technegydd? - Who is the technician?

• *Pwy sy'n dechnegydd? - Who is a technician?

• Pwy ydy Dewi Lingo? - Who is Dewi Lingo?

• Pwy sy'n dysgu Cymraeg yma? Who is learning/teaching Welsh here?

[frannyglass79]

Ah, diolch. Makes sense.

[EllisVaughan]

The sentence you suggest would actually be "Who is in the technician?".