initial

(noun): The first letter of a word or a name.
(noun): In plural, the first letter of each word of a person's full name considered as a unit.
(noun): A distinguished initial letter of a chapter or section of a document.
(noun): Onset, part of a syllable that precedes the syllable nucleus in phonetics and phonology.
(verb): To sign one's initial(s), as an abbreviated signature.
(adjective): Chronologically first, early; of or pertaining to the beginning, cause or origin.
(adjective): Spatially first, placed at the beginning, in the first position; especially said of the first letter of a word.

You can get your initials printed at the top.
Please initial each page and sign the contract in full at the bottom.
Our initial admiration for their efficiency gave way to disgust about their methods.
The initial letter of names is usually printed with a capital letter.