Celui-ci est mon livre.
English: This one is my book.
Simple demonstrative pronouns in French are words like 'celui', 'celle', 'ceux', and 'celles' used to point to or replace a previously mentioned noun.
Use these pronouns when you want to refer to something or someone that has already been mentioned, without repeating the noun. They are often used to show preference, make comparisons, or answer questions like 'Which one?'.
Celui-ci est mon livre.
English: This one is my book.
Celle-là est plus grande.
English: That one (feminine) is bigger.
Ceux que tu vois sont mes amis.
English: Those (masculine) you see are my friends.
Celles de Marie sont rouges.
English: Marie’s (feminine) ones are red.