An abjad is a type of writing system where each symbol always or usually stands for a consonant, leaving the reader to supply the appropriate vowel.

Abjad is thought to be based on the first letters (a, b, g, d) found in all Semitic languages such as Phoenician, Syriac, Hebrew, and Arabic. In Arabic, "A" (alif), "B" (bā’), "J" (jīm), "D" (dāl) make the word "abjad" which means "alphabet". The modern Arabic word for "alphabet" and "abjad" is interchangeably either "abajadīyah" or "alifbā’īyah". The word "alphabet" in English has a source in Greek language in which the first two letters were "A" (alpha) and "B" (beta), hence "alphabeta" (in Spanish and Italian, "alfabeto", but also called "abecedario", from "a" "b" "c" "d"). In Hebrew the first two letters are "A" (aleph), "B" (bet) hence "alephbet." It is also used to enumerate a list in the same manner that "a, b, c, d" (etc.) are used in the English language.