Another word to add to the vocabulary! Said in perfect context too - Granny & Granddad (Jones) were leaving and said goodbye and Archie said bye bye & waved. He later said it because Matt left the room.
Words so far: mummy, daddy, granddad, yeah, bye bye.
Signs so far: milk, music, more, banana, food/eat, tired, come.
Not bad for 11 months!