-ath

-ath is a Sindarin collective plural suffix, meaning all of the group to which it is affixed. It originated as a dual, and is sometimes still used as such.

Examples

• giliath
• Eglath
• Argonath (used as a dual)

References

• J.R.R. Tolkien; Humphrey Carpenter, Christopher Tolkien (eds.), The Letters of J.R.R. Tolkien, Letter 347, (dated 17 December 1972)
• J.R.R. Tolkien, "Notes and Translations": Commentary to "A Elbereth Gilthoniel", in The Road Goes Ever On, especially pages 72-3 (third edition).