or ac- or af- or ag- or al- or ap- or as- or at-
Etymology: Middle English, from Anglo-French & Latin; Anglo-French, from Latin, from ad — more at at
1. to ; toward — usually ac- before c, k, or q <acculturation> and af- before f <affluent> and ag- before g <aggradation> and al- before l <alliteration> and ap- before p <apportion> and as- before s <assuasive> and at- before t <attune> and ad- before other sounds but sometimes ad- even before one of the listed consonants <adsorb> 2. near ; adjacent to — in this sense always in the form ad- <adrenal>
New Collegiate Dictionary. 2001.