Noble

Noble is a state-privileged status which is generally hereditary. Titles of nobility are usually associated with present or former monarchies. The term originally referred to those who were "known" or "notable" and was applied to the highest social class in pre-modern societies.

One Piece
Nobles are not to be confused with World Nobles as nobles are people restricted to their respective kingdoms while the World Nobles are people who were descendants from the Twenty Kingdoms and live only in Mariejois.

A majority of the nobles shown in the series have been shown to be heartless. In particular, the nobles from Goa kingdom deciding to have Gray Terminal burned and shoot the people living there who tried to escape to make the kingdom beautiful for the visiting World Nobles, in hopes to be given a step up in their Noble status. They also believe that they are fools for reasons outside of their control, one key statement where a father told his daughter they were Trash and Fools because they were not born Noble. All nobles have been shown to be very cowardly, where despite their fearsome reputation they often cower to any threat of physical violence. They also seem to believe people are only interested in money, often bribing or suggesting money as a form of defense and if that doesn't work suggest the implications of harming them would cause, and will believe the person is insane if they do not accept the money or threat. In another words, they have no idea how the real world works outside their own petty and selfish reasons.

Currently the only people to whom this has not stretched to would be the rulers of the Kingdom of Alabasta, who truly care deeply for their people despite the differences in status and fight to protect them, going as far as self-sacrifice as well as consider blowing up their own castle. Wapol's Father, and later his successor Dalton, also only cared for the well-being of their people, and are loved by the kingdom in return. Sabo, who is deeply disgusted by the way Nobles act and wishes to have his status as one revoked, is another prime representation of a "kind" Nobility.

Trivia

 * Currently Dalton is the only Noble revealed who was not originally born as a Noble.