As-salamu alaykum! Welcome to EDITING ISLAM Chapter 2.
THIS traditional Muslim greeting means “Peace be with you.” The appropriate response is Wa alaikum assalaam (“and upon you be peace”). Interestingly, this is very similar to the Hebrew greeting Shalom aleikhem (“peace be upon you”) and response Aleikhem shalom (“upon you be peace”).
BECAUSE these Islamic greetings are phonetic translations of Arabic into English, any phonetic spelling may be correct. No definitive English spelling has been agreed upon. These words are not in the AP Stylebook. Google them and you will see many spellings, as with other Arabic words. The best thing to do is find out the spelling used by the publication for which you are working. In your own writing, you can use any spelling, just be consistent.