A knifelike device with a blunt edge, used for slicing letters open.

A letter that is written generically with blanks to be filled in with individual details, often sent in bulk, and frequently regarded as impersonal.

An aerogram; a letter sent by airmail.

(US) A letter mailed at a post office and either kept for general delivery, or delivered to a post office box, at that same post office.

An employee of the post office who delivers mail (post) to, and collects it from, a residence or business, or from public mailboxes.

(historical) The letter "A" in scarlet cloth required to be worn by those convicted of adultery in 17th-century Puritan New England.

An upper-case letter (A, B, C, ... as opposed to a, b, c, ...), used for emphasis, for starting sentences and proper names, etc.

(education) A letter of the alphabet assigned as an evaluation of schoolwork, with A generally being the best. Passing grades may also carry a plus or minus sign, with an A-minus (A-) better than B-plus (B+) and so on.

(UK, dated, euphemistic) A condom.

(nautical, historical) An official commission from a government authorizing someone to seize the property or people of another nation; especially to attack merchant shipping of another nation.