(Roman Catholic Church) a title given to a nun (and used as a form of address)
"the Sisters taught her to love God"
a female person who is a fellow member of a sorority or labor union or other group
"none of her sisters would betray her"
A daughter of the same parents as another person; a female sibling.
"When I visited the convent, Sister Mary welcomed me warmly and offered me some tea before showing me around the chapel."
Title of respect for an adult female member of a religious order.
In plain English: A sister is a girl who shares at least one parent with you.
"My sister lives in London and visits us every summer."
To strengthen (a supporting beam) by fastening a second beam alongside it.
"The foreman ordered us to sister the rotten floor joists before winter hit."
In plain English: To sister something means to connect two pieces of wood together using nails or screws so they stay firmly attached.
"The two sisters sat side by side and sang together during the choir performance."
Usage: Use this verb specifically in construction to describe reinforcing a structural member, such as a girder or joist, by nailing another piece of lumber directly beside it for added strength. Do not confuse this technical application with the familial relationship denoted by the noun form of the word.
The word sister comes from the Old English swustor, which originally meant both "sister" and "nun." It traveled into modern English through Middle English while retaining its core meaning of a female sibling.