- IPA(key): /ˈoːpa/ (standard)
- IPA(key): /ˈɔpa/ (chiefly western German)
- IPA(key): /ˈoːpʰɐ/ (some speakers from Kiel)
- Homophone: Oper 
- The word is commonly used with a definite article in most parts of central Germany, southern Germany, and Austria: Wo ist der Opa? – "Where is Grandpa?" In northern Germany—and generally in writing—no article tends to be used: Wo ist Opa?
- The genitive Opas is used before the modified term, without any article or determiner: Opas Tasche – “Grandpa’s bag”. This is chiefly northern German usage; the rest of the language prefers: die Tasche vom Opa (as above). — The genitive can also be used with an accompanying article or determiner: die Tasche meines Opas – “my grandpa’s bag”. This, however, is formal usage and Opa is rather rare in formal style; children will say instead: die Tasche von meinem Opa.
Declension of Opa
- Opa in Duden online