1sis·ter 
/ˈsɪstɚ/ noun
plural sis·ters /ˈsɪstɚ/ noun 1 [count] : a girl or woman who has one or both of the same parents as you
▪ my little/younger sister ▪ his big/older sister ▪ She's my twin sister. ▪ He has two sisters. — compare half sister, sister-in-law, stepsister 2 informal — used when talking to a woman ▪ Sister, you have got to relax. ▪ Sister, you don't need him in your life. 3 or Sister [count] : a member of a religious community of women : nun
▪ The sisters live in the convent. — often used as a title ▪ the Sisters of St. Joseph ▪ Sister Christine — abbr. Sr. 4 [count] : a woman who is from the same group or country as you
▪ her college sorority sisters ▪ We must support our brothers and sisters fighting overseas. ▪ She speaks for her Asian sisters. 5 [count] US, informal : a black woman — used especially by African-Americans 6 or Sister [count] chiefly Brit : a nurse in a hospital ward or clinic
▪ my little/younger sister ▪ his big/older sister ▪ She's my twin sister. ▪ He has two sisters. — compare half sister, sister-in-law, stepsister
▪ The sisters live in the convent. — often used as a title ▪ the Sisters of St. Joseph ▪ Sister Christine — abbr. Sr.
▪ her college sorority sisters ▪ We must support our brothers and sisters fighting overseas. ▪ She speaks for her Asian sisters.
— see also weak sister
