(Kyūshū or informal) It is indeed so. / Yes.

Polite form of だ (da), after uninflecting parts of speech: to be / After the plain past or nonpast form of -i adjectives (or nonstandardly verbs), to form the polite ending.

is, am, are

used to give an explanation or reason / used to give an emphasis or a special sense

Polite form of のです (no de su, used to indicate strong assertion).

(polite) Polite form of なのだ (na no da, used to indicate strong assertion).

(formal) Alternative form of だから (da kara)

expresses a reason or cause, results in a conclusion / used to emphasize a certain point / used to explain a situation or circumstance

Yes / It seems that (adjective/adjectival phrase) / That's right

seems like; looks like; I hear that