initial

The first letter of a word or a name.

In plural, the first letter of each word of a person's full name considered as a unit.

“You can get your initials printed at the top.”

A distinguished initial letter of a chapter or section of a document.

Onset, part of a syllable that precedes the syllable nucleus in phonetics and phonology.

To sign one's initial(s), as an abbreviated signature.

“Please initial each page and sign the contract in full at the bottom.”

Chronologically first, early; of or pertaining to the beginning, cause or origin.

“Our initial admiration for their efficiency gave way to disgust about their methods.”

Spatially first, placed at the beginning, in the first position; especially said of the first letter of a word.

“The initial letter of names is usually printed with a capital letter.”