Affixes

The Old English prepositions were originally separate words, but became reduced to a‑ and attached to the words they once modified. The process can be seen in alive, which in Old English was two words, on līfe, literally ‘in life’; others of similar type are aside, akin, and anew. Some examples are verbs derived from Old English a‑, which had an idea about it of an action or an intensification of an action: arise, abide, and awake.

Some adjectives imply a continuing or active state, and have much the same force as a present participle ending in ‑ing (see ‑ing²): ablaze, abuzz, afire, afoot, aglow, astride. Others combine the prefix with a present participle, usually hyphenated; such words imply an ongoing process or activity: a-brewing, a-roving, a-hunting, a-wasting; though they are mostly now archaic, literary, or dialectal, the form has had a small revival in recent decades, as in Bob Dylan's song lyric The times they are a-changing.