Eth, known as ðæt in Old English, is a letter used in Old English, Middle English, Icelandic, Faroese, and Elfdalian.
A sample of Icelandic handwriting with some instances of lowercase ð clearly visible: in the words Borðum, við and niður. Also visible is a thorn in the word því.
In a writing system, a letter is a grapheme that generally corresponds to a phoneme—the smallest functional unit of speech—though there is rarely total one-to-one correspondence between the two. An alphabet is a writing system that uses letters.
Ancient inscription on a vase featuring Greek letters
The American manual alphabet, an example of letters in fingerspelling
Engravings of decorated Latin letters, from the 18th century (note the lack of a J and a U)
Image: Decorated Roman alphabet MET DP855610