It might seem simple, but an "a" or an "an" before a word actually indicates a lot about the word's meaning. Derived from Latin, an "a" or "an" prefix often indicates the opposite or absence of something. For example, the word "anarchy" implies that something is without "archy," Latin for government. "Anonymous" means without a name and "atypical" means the opposite of typical, or rare.
Seeing "luc," "lum" or "lus" as a prefix or root implies that the word has something to do with light. "Luminous" means full of light. "Elucidate" means to shed light upon, or to make clear. "Luster," likewise, means a sheen or a glow, a quality produced by light, and "translucent" describes something that light can shine through.
While these two groups might seem similar, they're quite different and should not be confused. "Ver" or "veri" is a prefix derived from the Latin for truth. To "verify" means to find the truth. A "verdict" is a statement of the truth, as decided by a jury. "Vert" or "vers,' on the other hand, means to turn or to change. "Divert" means to turn away from, while "versatile" implies something can be easily turned or changed. The additional "s" after "ver" completely changes its meaning.
The GRE exam often uses words with the roots and prefixes "pug," "belle" and "belli." Each has a meaning that involves violence, war or conflict. "Antebellum," for example, means before the war, while "pugnacious" means eager or quick to argue or quarrel. "Belligerent" as a noun can refer to a participant in a war, while as an adjective it means combative or violent.
Because "pro" has many meanings, students often get confused. It can mean before, forward or positive. For example, the word "protrude" means to stick out or push forward from something else. The word "providential," however, is a positive event that happens at an opportune time. "Prophylactic" is the before form of "pro," a medicine taken to prevent a disease before it occurs.