What are mother and father in Japanese?

There are several words which mean mother and father in the Japanese language. It depends on the level of respect. I'd definitely recommend okasama and like the look of chichi.

The most common are 'okasan' (mother) and 'otosan' (father) - which are acceptable terms for a learner to use in most situations.

'Okasan' can become okasama (more formal) or 'kachan' (less formal). Similarly 'otosan' becomes 'otosama' or 'tochan'. 'Chichi' (father) and 'haha' (mother) can be used to refer to your own parents, but not to address your parents - and also in expressions such as 'Haha no hi' (Mothers Day). 'Hahaoya' (mother) and 'oyaji' (father) are also commonly used - but not as a form of address. 'Mama' and 'Papa' are becoming standard now as well. I'm sure there are more.