As a speaker of other languages which has a similar distinction between the polite form (vous in french) and the more informal (in this case, tu), it seems kind of weird to me that you would say vous to a person you are on sisterly terms with. Can somebody explain?
There is another possibility: "ma soeur" is the way you address a nun.
You would be right to show respect by the use the polite "vous", but you would ruin your credibility by trying to seduce her with such a compliment... My opinion, only!
Maybe in the old days, in noble families, it could have been correct (and even required) to express in such a polite form. Regardless, both answers should be correct, even if "vous" seems weird in this case.
Nuns are called sisters, but are they actually called "my sisters"? Anyway, to my ear this sounds like someone emphasizing the compliment by going for excessively formal, kind of same as someone using a full name even while being on close terms..."Miss N.N., how beautiful you are today!"
Yes, French Catholics address nuns with "ma soeur" and priests with "mon père".
Non-Catholics address nuns with "soeur Anne" (first name) and priests "père Dupont" (surname)
Soldiers address their officers with "mon capitaine, mon commandant, etc"
Civilians address officers with "capitaine, commandant, etc".
if her sister is beautiful , why is not you "lovely " also correct, cute is not the same a beautiful but lovely is , cute is also "American " and not English
Can someone explain to me why i found a few times different spelling of êtes? I came across êtes and êtez. What is the difference between the two?
Êtez is not correct. -ez is a usual form of verb in "vous" case, but as être is irregular, it is vous êtes. The only form.
Is it normal for someone to be so formal when speaking to a sister? I tried the more informal "est" but was marked as incorrect.
Both formal and informal versions are accepted, but the latter needs "tu es belle, ma soeur" ("est" is 3rd person singular).
It def isn't needed, but I can imagine one saying this when they see their sister in a wedding dress, to emphasise her maturity or so...
Why not "Tu es belle?" and that's it? If using "ma soeur" in speech, surely one would not use the possessive "ma" nor tell a nun she is beautiful. The sentence seems rather too Shakespearen or Tolstoy for 2018.
If I speak to a nun, I will call her "ma soeur, vous...". If she is beautiful, I may tell her.
If I speak to a priest, I will call him "mon père", vous...". If he is beautiful, I may tel him.
There is one discussion thread per sentence, but several possible exercises per sentence.
As a consequence, we don't know which exercise you had to do, even less what you suggested or what the computer checker responded.