Oma Opa vs. Großmutter Großvater
Is there a certain context to use Oma and Opa or does it not matter?
Opa und Oma = grandpa and grandma
Großvater und Großmutter = grandfather and grandmother
It all depends on if you want to address to them in a polite way or a colloquial way.
It´s rather like Mum and Dad vs. mother and father. If you are the child/grandchild you will probably use the informal version..
What about Großvatti vs Opa and Großmutti vs Oma? In school, I don't recall ever using Oma or Opa, but I don't think I've ever heard native speakers use Großvatti and Großmutti.
For me the versions with i sound a little childish, same with Pappi, Mammi, Opi, Omi but there are people who use them even in older age. I myself used Oma, Opa or the the old forms Ahne, Ehne which are out of use now it think.
To me they sound a combination of old-school and childish. I'm a native speaker and never heard anyone say Großvati and Großmutti, I only read it. It's Oma and Opa in informal context, sometimes Omi or Opi but that mostly to the grandparents themselves (it's like the difference between dad and daddy, but for grandparents).
Thanks for the response. Now I wonder why we learned the words Großvatti and Großmutti instead of Oma and Opa.....
Children have all sorts of nicknames for their grandparents -- different families often have different traditions.
So some might say Oma, some might say Omama, some might Omi, some Großmutti, etc. etc.
A bit like in English - some say nan, some nana, some granny, some grandma, etc.