妹妹 → ☊ 
em gái 
sister 
My younger brother and younger sister have three fishes. ☊ 
Em trai và em gái của tôi có ba con cá. ☊ Family like: Em gái → →
die Schwester ☊ chị, em gái ☊ 
☊ She doesn't play as well as her sister. ☊ as ☊
My sister's expecting a baby = she is pregnant. ☊ baby ☊
She's going to her sister's for the evening. ☊ evening ☊
He got his sister to help him with his homework. ☊ get ☊
go to do sth: She has gone to see her sister this weekend. ☊ go ☊
I'm going around to my sister's (= her house) later. ☊ go around/round (to...) ☊
'Couldn't you have just said no?' 'Well, hardly (= of course not), she's my wife's sister.' ☊ hardly ☊
my little brother/sister (= younger brother/sister) ☊ little ☊
She was far more intelligent than her sister. ☊ more ☊
I never knew (= didn't know until now) you had a twin sister. ☊ never ☊
She bears more than a passing resemblance to (= looks very like) your sister. ☊ passing ☊
She was chosen in preference to her sister. ☊ in preference to sb/sth ☊
scream (out) that...: His sister screamed out that he was crazy. ☊ scream ☊
an older/younger sister ☊ sister ☊
a big/little/kid sister ☊ sister ☊
My sister's coming to stay next week. ☊ stay ☊
She knew surprisingly little about her sister's life. ☊ surprisingly ☊
He gave it to his sister. ☊ to ☊
turn that...: It turned out that she was a friend of my sister. ☊ turn out ☊