Synonyms for Initial:

adj.

beginning (adjective)
hatching, aboriginal, opening, alpha, primeval, primary, emerging, first, new, sprouting, fundamental, inaugural, baby, preparatory, maiden, nascent, introductory, preliminary, early, beginning, primordial, embryonic, primal, Commencing, initiatory, infantile, original, infant, precursory, foremost, Inceptive, fetal, formative, Dawned, incipient, starting, budding, genesis, newborn, germinal.
earliest (adjective)
maiden, original.
early (adjective)
new, primeval, aboriginal, primordial, budding, primal, prime.
elementary (adjective)
beginning, primary, preliminary.
incipient (adjective)
start.
infant/infantile (adjective)
baby, newborn.
initial (adjective)
germinal, embryonic, foremost, original, incipient, introductory, pioneer, Inceptive, early, earliest, nascent, first, inaugural, opening, fundamental, infant, initiatory, Commencing.
in the beginning (adjective)
early.
original (adjective)
genuine, unique, novel, creative, authentic, innovative, first, original, ingenious, prototypical.

n.

junior, nee, namesake, by, naming ceremony, Of, after, nameless, assignment. at first, front end, leadoff, from the get-go, Inceptive, start, all along, initiatory. alphabetical, alphabetize, block capitals, block letters, letter, consonant, alphabet, capital. prime, sign away, sign, countersign, signature, ratify, sign on, earliest, John Hancock, pioneer, sign on the dotted line, endorse, witness, primary.

Other synonyms:

pioneer, earliest, naming ceremony, nee, endorse, alphabetical, front end, alphabet, Inceptive, all along, capital, block capitals, namesake, block letters, nameless, initiatory, alphabetize. junior, letter, consonant, opening. prime, Of. by. after. earliest
primary.
Other relevant words:
front end, at first, namesake, prime, alphabetize, countersign, Inceptive, fundamental, primary, junior, start, consonant, ratify, pioneer, initiatory, capital, nameless, endorse, sign, earliest, leadoff, opening, letter, alphabet.

Usage examples for initial

  1. I had scarce recovered from my initial surprise when another- more complete still- confronted me. – Castles in the Air by Baroness Emmuska Orczy
  2. And she took them on the initial advance. – Kelly Miller's History of the World War for Human Rights by Kelly Miller
  3. The two countries have more than the initial letter in common. – Rambles and Recollections of an Indian Official by William Sleeman