"sister" as noun
1 - A daughter of the same parents as another person; a female sibling.
2 - A female member of a religious order; especially one devoted to more active service; (informally) a nun.
3 - Any butterfly in the genus Adelpha, so named for the resemblance of the dark-colored wings to the black habit traditionally worn by nuns.
"sister" as verb
1 - To strengthen (a supporting beam) by fastening a second beam alongside it.
2 - To be sister to; to resemble closely.
