initial

nouns

the first letter of a word (especially a person's name)
"he refused to put the initials FRS after his name"
is a type of (narrower)
the conventional characters of the alphabet used to represent speech
"his grandmother taught him his letters"

verbs

mark with one's initials
entails
give sanction to
"I approve of his educational policies"
is a type of (narrower)
be engaged by a written agreement
"He signed to play the casino on Dec. 18"; "The soprano signed to sing the new opera"

adjectives

occurring at the beginning
"took the initial step toward reconciliation"
is similar to
preceding all others in time or space or degree
"the first house on the right"; "the first day of spring"; "his first political race"; "her first baby"; "the first time"; "the first meetings of the new party"; "the first phase of his training"