An abundance of wealth.

*Affluence* comes from the Latin verb *affluere,* “to flow abundantly.” Thus, someone or something blessed with affluence has received an incoming *flood* of riches. Since the *affluent* residents of suburbs often work in the central city but pay taxes back home, the wealth of some metropolitan areas tends to *flow* in one direction—out.

Polluting waste material discharged into the environment.

*Effluent* comes from the Latin verb *effluere,* “to flow out.” In an older meaning, an effluent was a stream flowing out of a river or lake. But nowadays *effluent* almost always means wastes that pour into our water and air. Liquid factory waste, smoke, and raw sewage can all be called effluents. An effluent filter keeps treated waste flowing out of a septic tank from clogging up its drainage pipes.

(1) A coming or flowing together at one point. (2) A place of meeting, especially of two streams.

The joining of rivers—as at Harpers Ferry, West Virginia, where the Shenandoah and Potomac Rivers flow together spectacularly—was the original meaning of *confluence*, and in its later meanings we still hear a strong echo of the physical merging of waters. So today we can speak of a confluence of events, a confluence of interests, a confluence of cultures, and so on, from which something important often emerges.

Flowing like honey; sweetened as if with honey.

With its root *mel-,* meaning “honey,” *mellifluous* means literally “flowing like honey.” The word usually applies to sound; it has often been used to describe voices such as Renee Fleming's or Barbra Streisand's, or pieces by composers such as Ravel and Debussy. The DJ on a radio station that plays soft music may have a voice so mellifluous that it almost puts the listener to sleep.

Adapted for grasping, especially by wrapping around.

Howler monkeys are among the American monkeys with prehensile tails. Famous for their booming howls, howlers can wrap their tails around a nearby branch while using their prehensile feet and hands for picking lice from their fur or lobbing a coconut at an unwelcome tourist. Our own hands are prehensile, of course. Our feet are not; on the other hand, they're much better for running than the prehensile feet of a monkey or ape.

(1) Arrest, seize. (2) Understand.

To *apprehend* is to seize, either physically or mentally. So to apprehend a thief is to nab him. But to apprehend a confusing news story, or to apprehend a difficult concept in physics, is to understand it—that is, to “grasp” it mentally. If you're *apprehensive* about something that's about to happen, it means you've grasped all the unpleasant possibilities and are waiting with anxiety or dread.

(1) To grasp the meaning of; understand. (2) To take in or include.

To comprehend is to mentally grasp something's complete nature or meaning. *Comprehend* is thus often a bit stronger than *understand*: for example, you may understand the instructions in a handbook without completely comprehending their purpose. *Comprehend*'s second meaning is much less common. Using that sense of the word, we could say that good manners comprehends (that is, includes) more than simple table etiquette, for example, or that true courage comprehends more than just physical showing off. And something *comprehensive* includes a great deal: so a comprehensive exam, for instance, includes all the material that was studied in the course.

Deserving stern criticism or blame.

From its prefix *re-,* meaning “back,” *reprehend* would mean literally “to hold back, restrain” ; but even the Latin version of the verb had come to mean “to scold, blame”—in other words, to restrain bad behavior by expressing disapproval. *Reprehensible* is applied to both things and people—that is, both the sin and the sinner. So a senator might be scolded for reprehensible conduct, but might also be called a thoroughly reprehensible person. And most of us would call dogfighting morally reprehensible, and would use the same word to describe those who put the dogs up to it.