What it is: Aleinu declares that Hashem alone is King of the whole world — and looks ahead to the day every person will recognize Him. It was first written for the Rosh Hashanah Musaf prayer; tradition attributes it to the Talmudic sage Rav (some later sources say Yehoshua). For centuries it has closed every prayer service.
When: at the end of Shacharit, Mincha and Maariv, every day. How: stand. At “Va’anachnu kor’im” (“we bend the knee and bow”), bend your knees and bow — the custom is to bow at these words. You can say it alone or with a minyan.
Aleinu — every wordHebrew · transliteration · English · Hear it
Aleinu is also part of the full prayers: Shacharit · Mincha · Maariv.