The Irish Alphabet, Ancient, consists of two forms of writing: Ogam (4 letters) and Ogham (5 letters). Ogam is an alphabet that was used to write Primitive Irish between the 4th and 6th centuries AD. It is composed of a series of notches and strokes on the edge of a stone or wood. Ogham is a later form of writing which was used to write Old Irish between the 4th and 10th centuries AD. It is composed of a series of lines and notches cut into the edge of a stone or wood.