Aicmi (Ogham Groups)

Citation Formats

General Reference

Divinity Atlas. "Aicmi (Ogham Groups)." Accessed August 30, 2026. https://dev-divinity.interactiveatlas.org/categories/aicmi-ogham-groups.

APA Style

Divinity Atlas. (n.d.). Aicmi (Ogham Groups). Retrieved August 30, 2026, from https://dev-divinity.interactiveatlas.org/categories/aicmi-ogham-groups

BibTeX

@misc{divinityatlas-aicmi-ogham-groups,
  author = {Divinity Atlas},
  title = {Aicmi (Ogham Groups)},
  year = {2026},
  url = {https://dev-divinity.interactiveatlas.org/categories/aicmi-ogham-groups},
  note = {Accessed August 30, 2026}
}

The ogham alphabet's letters are arranged in groups of five called aicmi (singular aicme), each named after its first letter. The classical alphabet has four aicmi of five letters; a fifth group, the forfeda, was added later to write sounds the original set did not cover. The grouping is structural, since each aicme shares a stroke direction relative to the stemline.

Facts

Structure

Each aicme is a set of five letters sharing one way of placing the strokes relative to the stem-line, so a letter's group can be read at a glance from how its strokes sit. 1

Overview

Size of the Traditional Set

Four aicmi of five letters each in the classical alphabet, with a fifth group of five forfeda added later 1

Origins

Origin of the Name

Old Irish aicme, "family, class"; each group is named after its first letter. 1

Learn More

The Groups of the Ogham Alphabet

The letters of the ogham alphabet are arranged in groups of five called aicmi (singular aicme), each named after its first letter. The classical alphabet has four aicmi of five letters each (the aicme of Beithe, of Huatha, of Muine and of Ailme), making twenty letters, cut respectively below, above, across and through the stem-line.

The grouping is not merely alphabetical order but a structural feature of the script: the four aicmi correspond to the four ways a stroke can be placed relative to the line, so a reader can tell a letter's group at a glance from how its strokes sit.

The forfeda

A fifth group, the forfeda or supplementary letters, was added later to write sounds, chiefly diphthongs and non-native sounds, that the original twenty letters could not represent. These are more elaborate in form and appear mainly in the manuscript tradition rather than in the early stone inscriptions.

The atlas treats each aicme as a unit, giving its member letters and their shared placement, alongside the individual letters in their own category. The wider ogham system, and the medieval tree-lore attached to it, are treated under the ogham and letter categories.

Cross-Tradition Connections