Definition of a- :
A, as a prefix to English words, is derived from various sources. It frequently signifies on or in ( from an, a forms of AS. on), denoting a state, as in afoot, on foot, abed, amiss, asleep, aground, aloft, away ( AS. onweg), and analogically, ablaze, atremble, etc. AS. of off, from, as in adown ( AS. ofd/ ne off the dun or hill). AS. a- ( Goth. us-, ur-, Ger. er-), usually giving an intensive force, and sometimes the sense of away, on, back, as in arise, abide, ago. Old English y- or i- ( corrupted from the AS. inseparable particle ge-, cognate with OHG. ga-, gi-, Goth. ga-), which, as a prefix, made no essential addition to the meaning, as in aware. French a ( L. ad to), as in abase, achieve. L. a, ab, abs, from, as in avert. Greek insep. prefix / without, or privative, not, as in abyss, atheist; akin to E. un-.