"Dear Seth" would be the greeting.
salutation
Dear Mr. President is a salutation of a business letter. The salutation goes at the beginning, thus that's how you got Dear.
That part of the letter is called the salutation or greeting.
greeting
greeting
That part is known as the SALUTATION or GREETING.
The body of the letter is the part between 'Dear...' and 'Sincerely,'.
An example of a greeting of a letter, also known as the salutation, is "Dear Sir,"
Example:Letter Dear ______, ____________________________________ ________________________________________ ________________________________________ ________________________________________ Sincerely, ________ (P.S. __________________________________) Note: The P.S. part is optional
greeting
Sending a letter
Dear All