An old English word for a Muslim (as a noun) or for something Islamic (as an adjective). English made it in the 1600s from Mohammed + -an, from the earlier form Mahometan — the same pattern as Christian from Christ. Though actually, that pattern is exactly why many Muslims dislike it. Christians, in their faith, follow Christ as central in a way that is not the same as how Muslims honour Mohammed: Muslims do not worship Mohammed as God. They follow Islam, and they honour Mohammed as a prophet. So Mohammedan can sound as if English speakers renamed someone else's religion after a person, in a Christian shape. Today the ordinary, respectful words are Muslim and Islamic. You will still meet Mohammedan in old books, old translations, and some historical writing. Do not use it for people living now unless you are quoting.

「穆罕默德教徒」（舊稱，多數穆斯林覺得冒犯；現在說「穆斯林」。中文舊稱「回教徒」是另一套說法，不是這個英文詞的對譯）