عليه السلام / عليهم السلام
ʿalayhi l-salām / ʿalayhim al-salām
“Peace be upon him” or “upon them”: said when a prophet other than Muhammad is mentioned by name, and abbreviated AS in writing.
What it means
The words are a prayer for peace on a prophet. Muslims say them when they name a prophet other than Muhammad (peace be upon him), and in writing they abbreviate them to AS. The Quran uses the same words for earlier messengers: “Peace be upon Noah among the worlds” (37:79), “Peace be upon Abraham” (37:109) and “Peace be upon Moses and Aaron” (37:120). For Muhammad the fuller formula ṣallā llāhu ʿalayhi wa sallam is used. Each formula honours the prophet named and keeps the memory of the whole line of prophets.
Often misunderstood as
The abbreviation (AS) is often copied without it being known that it stands for a prayer of peace.
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 59, listed as ‘ALAYH AL SALĀM OR ‘ALAYHIM AL SALĀM (AS). The definition is restated here.