Eth (/ɛð/ edh, uppercase: ⟨Ð⟩, lowercase: ⟨ð⟩; also spelled edh or eð), known as ðæt (that) in Old English, is a letter used in Old English, Middle English, Icelandic, Faroese (in which it is called edd), and Elfdalian alphabets.
It was also used in Scandinavia during the Middle Ages, but was subsequently replaced with ⟨dh⟩, and later ⟨d⟩.