Ogham is an alphabet that appears on monumental inscriptions dating from the 4th to the 6th century AD, and in manuscripts dating from the 6th to the 9th century. It was used mainly to write Primitive and Old Irish, and also to write Old Welsh, Pictish and Latin. It was inscribed on stone monuments throughout Ireland, particuarly Kerry, Cork and Waterford, and in England, Scotland, the Isle of Man and Wales, particularly in Pembrokeshire in south Wales.
The name Ogham is pronounced [ˈoːm] or [ˈoːəm] in Modern Irish, and it was spelt ogam and pronounced [ˈɔɣam] in Old Irish. Its origins are uncertain: it might be named after the Irish god Ogma, or after the Irish phrase og-úaim (point-seam), which refers to the seam made by the point of a sharp weapon. Ogham is also known as or ogham craobh (tree ogham) beth luis fearn or beth luis nion, after the first few letters.
Ogham probably pre-dates the earliest inscriptions - some scholars believe it dates back to the 1st century AD - as the language used shows pre-4th century elements. It is thought to have been modelled on or inspired by the Roman, Greek or Runic scripts. It was designed to write Primitive Irish and was possibly intended as a secret form of communication.
While all surviving Ogham inscriptions are on stone, it was probably more commonly inscribed on sticks, stakes and trees. Inscriptions are mostly people's names and were probably used to mark ownership, territories and graves. Some inscriptions in primitive Irish and Pictish have not been deciphered, there are also a number of bilingual inscriptions in Ogham and Latin, and Ogham and Old Norse written with the Runic alphabet.
- Type of writing system: alphabet
- Number of letters: 25, which are grouped into five aicmí (sing. aicme = group, class). Each aicme is named after its first letter. Originally Ogham consisted of 20 letters or four aicmí; the fifth acime, or Forfeda, was added for use in manuscripts.
- Writing surfaces: rocks, wood, manuscripts
- Direction of writing: inscribed around the edges of rocks running from bottom to top and left to right, or left to right and horizontally in manuscripts.
- Letters are linked together by a solid line.
- Used to write: Primitive and Old Irish, Pictish, Old Welsh and Latin