An alphabet of strokes

Ogham is an alphabet of strokes cut across a stem-line, used to write Primitive Irish in inscriptions on standing stones, chiefly in Ireland and western Britain, from roughly the fourth to the sixth centuries CE. Each letter is one to five strokes, placed above, below or across the line, and each has a name.

The surviving stone inscriptions are mostly names and memorials. Medieval Irish scholars later elaborated the alphabet in manuscript tradition, attaching to each letter a tree, a bird, a colour and other associations in lists preserved in texts such as the Auraicept na n-Eces and the Book of Ballymote.