The fourth letter of the Latin alphabet. The Semitic letter Dâlet probably developed from the logogram for a fish or a door. In Semitic, Ancient Greek (Modern Greek /ð/) and Latin the letter was pronounced /d/, in the Etruscan alphabet the letter was superfluous but still maintained (see letter B). Greek letter: &Delta (capital) or δ (small) (Delta). Delta represents the letter D in the NATO phonetic alphabet.

In Cantonese, the sound /d/ means a little bit, from the ancient use of the character 的 (in the phrase "兀的") in Chinese written language. Since 的 is no longer used in this way, Hong Kong residents invented a new character 啲 (which is not supported in many Chinese systems), or simply write D instead.

In context, D is also:

• The symbol of deuterium, an isotope of hydrogen.
• A musical note
• The Roman numeral for 500
• The stock symbol for Dominion Resources Inc. VA
• A standard size dry cell battery.
• a programming language; see D programming language.
• The variable d for diameter of a circle.
• The symbolism for the differential operator.

• da db dc dd de df dg dh di dj dk dl dm dn do dp dq dr ds dt du dv dw dx dy dz