Question

Define an acid a base

Answer 1

Acid -sour in taste. Turn to red litmus
Base -bitter in taste.turn to blue litmus.

Answer 2

ACID- its a substance which is acidic in nature. it's determined so because of some of its properties which include the changing of litmus into red , sour taste  , pH lower than 7 ,etc. 

BASE-its a substance which is basic in nature. it's determined so because of some of its properties which include the changing of litmus into blue , bitter taste  , pH above 7 ,etc.