Él se la imagina delgada.

[mwtzzz]

He has never seen her; he has only talked to her on the phone. He imagines her to be thin. We say "El se la imagina delgada."

What is the purpose of "se" here?

[AngelicaDeAlquezar]

One can perfectly say "él la imagina delgada", and the sentence wouldn't change its meaning, but the pronominal is probably emphasizing that it's his own imagination.

I think it's a collocation though; we tend to use far more often "imaginarse" than "imaginar".

-- Estoy muy cansada. No dormí en toda la noche.
-- Me imagino. (I understand.)

- Ni te imaginas de qué color me pinté el cabello.

- Don Juan, ¿se imagina cómo habría sido su juventud con un teléfono celular?

- ¿Se imaginan si mi papá se entera de que estoy con ustedes?



I use "imaginar" mostly for more formal contexts and for concrete things that have been imagined:

- El pintor imaginó un mundo caótico sacado de las peores pesadillas.