Noble vs. hidalgo
The Spanish words 'noble' and 'hidalgo' have similar meanings related to nobility, but they are used in slightly different contexts.
Noble
This word is used in Spanish to denote someone from the noble class or possessing qualities that are considered noble. It can be both a noun and an adjective.
Es un hombre noble que ayuda a los demás.
(He is a noble man who helps others.)
El castillo era el hogar de una familia noble.
(The castle was the home of a noble family.)
Hidalgo
'Hidalgo' is a term specifically used to refer to someone from the lower nobility or gentry in Spain. The word traditionally referred to someone who was free from manual labour because of their noble birth.
Él es un hidalgo de una pequeña ciudad española.
(He is a hidalgo from a small Spanish town.)
El protagonista en la novela es un hidalgo pobre.
(The protagonist in the novel is a poor hidalgo.)
Summary
'Noble' and 'hidalgo' both relate to nobility but vary slightly in their use. While 'noble' refers broadly to someone of noble status or character, 'hidalgo' denotes a person from the lower aristocracy and historically indicated those exempt from manual work due to their birth.