Meaning of A- in English

A-

I. a- 1 /ə/ BrE AmE prefix

1 . in a particular condition or way:

aloud

alive (=living)

with nerves all a-tingle (=tingling)

2 . old use in, to, at, or on something:

abed (=in bed)

afar (=far away)

II. a- 2 /eɪ, æ, ə/ BrE AmE prefix

not or without:

amoral (=not moral)

atypically (=not typically)

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.