taskwazen

Japanese writing is very difficult, on the level of Egyptian hieroglyphics, so the same kanji (Chinese character) can be pronounced differently depending on the word. お祖父さん ojiisan means grandfather when talking about someone else's grandfather, and 祖父 sofu means grandfather when talking about your own grandfather. Notice that the character 祖 is pronounced differently in the two words "ji" in one and "so" in the other.