11th day to Balance 10 Senses in Body

Ekadasi generally falls on the 11^th day after the new moon, and the 11^th day after the full moon. Eka means one and dasi is the feminine form of dasa, which means ten. Together it means eleven. Only occasionally may it fall on a different day.

http://knowingbody.blogspot.com/search/label/Senses