say it: SI-stur
sister is a noun meaning "a female person who has the same parents as another person". It carries 3 recorded senses.
a female person who has the same parents as another person
“my sister married a musician”
(Roman Catholic Church) a title given to a nun (and used as a form of address)
“the Sisters taught her to love God”
Roman Catholic
Forms marked · are formed by the regular rule rather than recorded in the source data. English keeps a few hundred irregulars and the rest follow the pattern, so the rule is right far more often than not — but it is a rule, and the mark says so.
Definitions, synonyms and semantic relations for sister come from Princeton University’s WordNet. The pronunciation comes from the CMU Pronouncing Dictionary. Commonness is measured against a corpus of everyday English. Full sources and licences.