*Parameter *is a limit that affects how something can be done, and *perimeter* is the outline of a physical area. Both words have special meanings in math, but they take off their pocket protectors and relax their definitions when they join the rest of us.

*Parameter *is the fancier math and science word. In mathematics, *parameter* is a measurable factor in a system. Outside of math, *parameter* is still a factor, property, or characteristic. It can also be a boundary or a limit. Here are some examples:

That makes it the heaviest observed elementary particle yet discovered, but within the

parametersset by the Standard Model. (Scientific America)"As hard as journalism is, at least you have

parameters," she said. (New York Times)Within those

parameters, Ms. Gray played with color, creating an upbeat show reflecting London's mad, mad fashion world. (New York Times)

In mathematics, the *perimeter* is the boundary of a geometric figure. In mainstream language, it can be the limit of any physical area, often one protected by an armed force: secure the *perimeter!* Here are some examples from the news:

Police set up a

perimeteraround the house and blocked off Avery Street for safety reasons, Sgt. Scott Custer said. (Inquiring News)Newest study finds fuel spill's

perimeterexpanding. (KOB-TV)

Some linguistic snobs don't like *parameter*'s meaning of a boundary or limit when *perimeter *would do. But according to *Garner's Modern American Usage*, the use of *parameter* to mean boundary is "virtually universal" except by "die-hard snoots." Unless you are writing for such an audience (a math professor, perhaps), you can use *parameter* to mean boundary.

Just remember: The *parameters* of playing hide-and-seek are not peeking while you count, and to stay within the *perimeter* of the yard when you hide.