Delgado vs. flaco vs. esbelto

In Spanish, words like 'delgado', 'flaco' and 'esbelto' all describe body types related to slimness or thinness, but they have different connotations and uses.

Delgado

'Delgado' refers to being slim or slender in a healthy and often attractive way. It suggests a balanced body shape without excess weight.
Mi hermano es más delgado que yo.
(My brother is slimmer than I am.)
Ella tiene una figura delgada pero fuerte.
(She has a slim but strong figure.)

Flaco

'Flaco' is used to describe someone who is very thin, potentially to the point of looking undernourished or weak. It often carries a less positive connotation than 'delgado'.
Después de la enfermedad, quedó muy flaco.
(After the illness, he became very skinny.)
El perro abandonado estaba flaco y hambriento.
(The abandoned dog was skinny and hungry.)

Esbelto

'Esbelto' describes a person (or sometimes an object) that is slender in an elegant and graceful manner. It's often used to emphasize beauty, height, and poise.
La bailarina era alta y esbelta.
(The dancer was tall and slender.)
Ese edificio es asombrosamente esbelto.
(That building is amazingly slender.)

Summary

'Delgado', 'flaco' and 'esbelto' are all Spanish adjectives describing thinness, each with its own nuance of meaning. 'Delgado' implies a healthy slenderness, 'flaco' indicates being very thin, often not in a positive sense, and 'esbelto' highlights an elegant slenderness. Choosing the right word depends on the context and the quality you want to convey.