Actually there is a difference: > Cette lettre est à ma fille > *This letter belongs to my daughter* It is her property, but we don't know who wrote it. The sentence focus on the owner, not the writer. The other form can be ambiguous: > Cette lettre est celle de ma fille It could mean both: > *This letter belongs to my daughter.* > *This is a letter from my daughter.* However, without further information, the second meaning is the most likely. **EDIT:** [Luke's comment](https://french.stackexchange.com/questions/33037/is-there-any-difference-between-celui-and-%c3%a0-to-mean-possession/33038#comment67805_33038) add some precious information: > Cette lettre est celle de ma fille Can also be seen as an emphasis on *this letter* regarding some others that could be there. It could then be translated to: > *This letter is the one that belongs to my daughter.* > *This letter is the one written by my daughter.*