Joos differentiated five grades of formality in English: Frozen, Formal, Consultative, Casual and Intimate.
These styles of English are not all widely used. The frozen style is mostly used on ceremonies. The intimate style is used between family members and very close friends. The following sentences all express the same fact, but they vary in formality:
My father has deceased to join the heavenly choir.
My father has passed away.
My father has died.
My dad has died.
My old man just kicked the bucket.
As the example show, the levels of formality are mainly distinguished by the choice of words. The stylistic differences of words are in marked in contemporary dictionaries.