- panecillo (Although this one has most of the time another meaning...)
I know short question, but seemingly difficult for me. Is there a definitive diminutive form?
Are there multiple accepted forms?
In Mexico is well addressed as panecito, and I think anyone would understand it, however is not a real word as far as I know, at least couldn't find it on the dictionary, I found this however:
Here in Perú I was taught and learned it this way:
I memorized the key: "REN(cito)" -- Meaning when a word ends in "R", "E" or "N" append "-cito" (masculine) or "-cita" (feminine). Otherwise, words ending in "O" or "A" likely get "-ito" (masculine), "-ita" (feminine), or seemingly less common "-illo" (masculine) and "-illa" (feminine).
Therefore, and confirmed by what is practiced here in Hauncayo, Perú we say Pancito to refer to a smaller piece of bread or smaller roll.
Panecillo (a small bread baked in that form, not a slice) is itself a word. You could say "panecillito" for a small "panecillo".
So, for "pan" (any kind of "bread") I would say "pancito" or "panecito". "Pansito" and "panesito" are wrong.
"Pan" is a generic term, it means bread in general, not an actual piece of bread. In this sense you would not use it in diminutive form, would you?