SHEMONEH ESREH (Heb. שְׁמוֹנֶה עֶשְׂרֵה; lit. "eighteen"), popular name for the *Amidah prayer. The name stems from the fact that the weekday Amidah originally contained 18 benedictions (although today none of the various Amidot recited on different occasions consists of exactly 18 benedictions).
"Shemoneh Esreh." Encyclopaedia Judaica. . Encyclopedia.com. (January 22, 2019). https://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/shemoneh-esreh
"Shemoneh Esreh." Encyclopaedia Judaica. . Retrieved January 22, 2019 from Encyclopedia.com: https://www.encyclopedia.com/religion/encyclopedias-almanacs-transcripts-and-maps/shemoneh-esreh