a-

Multiple Entries:
  a-    ad-  

Concise Oxford English Dictionary © 2008 Oxford University Press:
a-1 (often an- before a vowel)

▶prefix not; without: atheistic.

– origin from Gk.

Concise Oxford English Dictionary © 2008 Oxford University Press:
a-2

▶prefix

• 1 to; towards: aside.

• 2 in the process of: a-hunting.

  ■ in a specified state: aflutter.

– origin OE, unstressed form of on.

Concise Oxford English Dictionary © 2008 Oxford University Press:
a-3

▶prefix variant spelling of ad- before sc, sp, and st (as in ascend, aspire and astringent).

Concise Oxford English Dictionary © 2008 Oxford University Press:
a-4

▶prefix

• 1 of: anew.

• 2 utterly: abash.

– origin unstressed form of of (sense 1); Anglo-Norman Fr. a-, from L. ex (sense 2).

Concise Oxford English Dictionary © 2008 Oxford University Press:
ad- /ad/ (also a- before sc, sp, st; ac- before c, k, q; af- before f; ag- before g; al- before l; an- before n; ap- before p; ar- before r; as- before s; at- before t)

▶prefix

• 1 denoting motion or direction to: advance.

• 2 denoting reduction or change into: adulterate.

• 3 denoting addition or increase: adjunct.

– origin from L. ad ‘to’.