Familiar, affectionate term for one's own older sister. Also used to address a young woman informally, similar to 'miss' or 'big sis'.
See also: 姉さん
My little brother is always clinging to our big sister.
My older sister is a university student.
Hey miss, how much is this outfit?
Informal way to refer to or address a young woman, often by a male speaker. Can sound rough or overly familiar depending on context.
That girl is cute.
The neighborhood kids call her 'big sis'.
妹 means 'younger sister', the direct opposite of 姉ちゃん's 'older sister' sense.
姉さん is a more polite, respectful way to refer to or address an older sister or young woman, while 姉ちゃん is casual and affectionate.
お姉さん is the polite, everyday term used to address an older sister or an unfamiliar young woman, whereas 姉ちゃん sounds more familiar or rough.
兄ちゃん refers to an older brother (or young man), while 姉ちゃん refers to an older sister (or young woman); learners can mix up the gender.
Derived from 姉 (ane, 'older sister') with the familiar suffix ちゃん (chan). The reading ねえちゃん reflects a colloquial contraction of あね to ねえ.