These are exclamations that do not fit the syntactic rules of the other parts of speech, hence their classification among the particles. All interjections end with the same vowel, either naturally,

ta t um

ti’a Ta oh!

or because the interjection marker -a /a has derived them from nouns or verbs.

mica Mc hello

nara nr goodbye; good night

hacca h;c good morning

kica Kc what?

hira Hr please; thank-you