Ad- ::
Ad- () As a
prefix ad-
assumes the forms ac-, af-, ag-, al-, an-, ap-, ar-, as-, at-,
assimilating the d with the first
letter of the word to which ad- is
prefixed. It
remains unchanged before vowels, and
before d, h, j, m, v.
Examples: adduce, adhere, adjacent, admit, advent, accord, affect, aggregate, allude, annex, appear, etc. It
becomes ac-
before qu, as in
acquiesce..