姐 vs 姊, etymology, and their English equivalences

Question

Sometimes 姐 and 姊 are interchangeable, sometimes 姐 and 姊 have different meanings.

Can we summarize their usages? What is their etymology? And can we find their English equivalences?

It looks that 姐 has something to do 祖 with the same 且. The 且 has something to do with the tombstone or the male reproductive/sex organ.

But it seems counter-intuitive that:

姊 is used for the senior sister.

姐 can be used for both junior or senior female.

小姐 means Lady. Like "各位小姐先生" means "Ladies and Gentlemen."

(祖, in contrast, is always used for the senior person or the ancestors.)

Answer 1

「姐」 (Zhengzhang OC: /*ʔsjaːʔ/, mother > senior female > adult female, elder sister) is comprised of semantic 「女」 (female) and phonetic 「且」 (/*sʰjaːʔ/). Through its semantic extensions, 「姐」 has developed into many uses:

• The meaning big sister is roughly equivalent to English big sis', more commonly used in colloquial spoken language;

• The meaning mother is no longer found in Standard Mandarin, but is preserved in some other topolects;

• All other meanings are from an extension of adult female. Your reading of 「小姐」 does not imply that 「姐」 means junior female, but rather the prefix 「小」 being used as a term of endearment. Please see the question At what age is it inappropriate to call people 小李, 小王, 小刘, etc.? And is it different for males and females? for an idea of how 「小」 works.

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In contrast, 「姊」 (/*ʔsiʔ/, elder sister) is comprised of semantic 「女」 and phonetic 「𠂔」*. The meaning elder sister is frozen, and is the literary vocabulary used in writing the word for elder sister.

_{*「𠂔」 is inferred to be similar in sound to 「次」 (/*sn̥ʰis/) through readings of oracle bone inscriptions.}

Answer 2

姊 means 女兄, the older sister. Its usage is simple and pure.
Reiterative locution is not allowd when we use 姊. 姊姊 is not correct.
And we rarely use 姊 nowadays.
姐 has rich usages. It was from Sichuan dialect. The usages are as follows:
1. Same as 姊, 姊妹=姐妹， 姊=姐,姐姐， 阿姊=阿姐
2. It means mother in Song Dynasty. We don't use it now
3. It means the female. 大姐(the female who is older than you), 小姐姐(a female person, usually older than you, who’s somewhat mature but also young and cute at the same time.), 小姐(Young Lady)