Meaning of “dear” - Learner’s Dictionary

dear

adjective uk us /dɪər/
IN LETTERS

A1 used at the beginning of a letter, before the name of the person you are writing to:

Dear Amy
Dear Mrs Simpson
Dear Sir/Madam
LIKED [ always before noun ]

B2 A dear person is someone who you know and like very much:

my dear Peter
He's one of my dearest friends.
EXPENSIVE UK

expensive:

I wouldn't buy anything there, it's far too dear.
dear to sb/sb's heart

If something is dear to someone or dear to their heart, it is very important to them:

The charity was very dear to his heart.

(Definition of “dear adjective” from the Cambridge Learner’s Dictionary © Cambridge University Press)