Use of C'est

Question

In the following sentence - C'est ma sœur., c'est is not followed by un/une/la/le/les then why cant we use elle est?

Accepted Answer

Bonjour Meghna,
You're correct that it is not followed by a definite article (la/le/les) or an indefinite (un/une). However, it is still followed by determinant: possessive adjective (ma = my).
You use c'est in sentences it/he/she is + a/the/my... + [noun/name]. You use "c'est" if "it/he/she is" is followed by any form of article / determinant.

C'est la fille de Marie. = She is Marie's daughter.
C'est un chien. =It's a dog.
C'est ma vie ! = It's my life!
C'est son pantalon préféré ! = It's his/her favourite pair of trousers!

I hope this is helpful.
Bonne journée !