<human>:  When did the letter a come into existence?
<bot>: The letter a comes from the Latin word ad, meaning “to” or “towards”. The letter a was originally a ligature of the letters ad, which were originally a ligature of the letters d and t. The letter a was originally a ligature of the letters d and t, but the letter t was later dropped from the alphabet, so that the letter a was no longer a ligature. The letter a came into existence in the year 1 A.D.