diff btwn vice, deputy &addl

can anyone clarify my doubt please?

what is the difference between vice, deputy, additional ?

like everywhere im getting the same answer they mean the same then why 3 differnt words are we using like we are taught vice president and not deputy or addl president , deputy speaker we say but we are not used to say vice speaker or addl speaker .

note: as per some provisions that i read in constitution ,there it was mentioned only about deputy speaker of state legislature and it is not mentioned as"VICE SPEAKER" or  "ADDITIONAL SPEAKER" (i dont know if the other two words' usage is acceptable or no)

THANKS IN ADVANCE.