AD- n.
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.
ADHERE v.
To hold, be attached, or devoted; to remain fixed, either by personal union or conformity of faith, principle, or opinion; as, men adhere to a party, a cause, a leader, a church.