
A sister is a
woman or a
girl who shares one or more parents with another individual; a female sibling.
The male counterpart is a
brother. Although the term typically refers to a
familial
Familial may refer to:
* ''Familial'' (album), a 2010 studio album by Phil Selway
*Family, a group of people affiliated by consanguinity, affinity, or co-residence
*Family (biology), one of the eight major taxonomic ranks, classified between orde ...
relationship, it is sometimes used endearingly to refer to non-familial relationships. A full sister is a
first degree relative
A first-degree relative (FDR) is a person's parent (father or mother), full sibling (brother or sister) or child. It constitutes a category of family members that largely overlaps with the term nuclear family, but without spouses.
If the persons ...
.
Overview

The English word ''sister'' comes from
Old Norse systir which itself derives from Proto-Germanic *swestēr, both of which have the same meaning, i.e. sister. Some studies have found that sisters display more traits indicating jealousy around their siblings than their male counterparts,
brothers. In some cultures, sisters are afforded a role of being under the protection by male siblings, especially older brothers from issues ranging from bullies or sexual advances by womanizers. In some quarters the term ''sister'' has gradually broadened its colloquial meaning to include individuals stipulating kinship. In response, in order to avoid equivocation, some publishers prefer the usage of ''female sibling'' over ''sister''. Males with a twin sister sometimes view her as their female alter ego, or what they would have been like, if they had two X chromosomes. A study in Perth Australia found that girls having only youngers brothers resulted in a ''chastity effect'', losing their virginity on average more than a year later than average. This has been hypothesized as being attributed to the pheromones in their brothers' sweat and household-related errands.
Sororal relationships
Various studies have shown that older sisters are likely to give a varied gender role to their younger siblings as well as being more likely to develop a close bond with their younger siblings.
[Gender — Page 53, Leanne Franklin – 2012] Older sisters are more likely to play with their younger siblings. Younger siblings display a more needy behavior when in close proximity to their older sister and are more likely to be tolerant of an older sis