What is a salutation and complimentary close as used in a business letter and personal business letter?

The salutation for a business letter should always be formal, even if the business letter is to someone you know well. Examples:

Dear Sir/Madam,

Dear Mr. Shepard,

Dear Ms. Huang,

Dear Prof. Sampson,

Sales Manager,

To Whom It May Concern,

The close of a business letter should always be formal as well:

Sincerely,

Very Truly Yours,

Most Sincerely,

Yours Truly,

The salutation for a personal letter is determined by your relationship with the recipient of the letter and can be formal or very casual. Examples:

Hi Mom,

Dear Aunt Anna,

Hey Rollie,

Sweetie,

Dear Friends,

Fred and Ginger,

The close of a personal letter can also be formal or informal. You can close with Words much like you would use if you were speaking to that person.