When we know the meaning of any part of a word, it can often lead us to understand the whole word.

The prefix "bi-" is a good example, and its definition, "two," partners well with a number of root words.

A bilingual speaker uses two languages and may present a bilateral argument, one having two sides.

Perhaps you recall celebrating our country’s bicentennial in 1976 — 200 years after the signing of the Declaration of Independence in 1776.

Biracial families, consisting of two races, have become more common, but bigamy, marriage to two people, is still illegal in most areas.

We have bicuspids, two-pointed teeth located between the canines and molars.

We sometimes flex our biceps, muscles having two points of origin.

And we, as bipeds, have two feet, and we often enjoy a spin on a bicycle, a human-powered vehicle mounted on two wheels.

A rather formal-sounding verb is "bifurcate," to divide into two parts. And a very simple noun, "bikini," refers to a woman’s brief, two-piece bathing suit.

It might be easy to confuse "biannual" and "biennial." The former describes an event that occurs twice each year, while the latter refers to something that lasts for two years or happens every other year. It can also describe a plant that completes its life cycle and dies in its second year. I remember it by thinking “e” as in "every other."

If you are writing about government, you can describe a bicameral legislature as one composed of two branches. A bipartisan body consists of or is supported by members of two parties.

Of course, “bi” beginnings are not always making reference to two. If a word begins with "bio-," you may be looking at the meaning, "life." "Biology" is the study of life, while "biography" is a writing about a life and an "autobiography" is a written piece about one’s own life.

There are many more words that use either bi- or bio-, and I like to think of them sort of working together. After all, in most species, doesn’t it take two to create life?

— Sandi Ekberg taught high school English in Medford for 30 years, with a special interest in vocabulary, grammar and usage. If you have grammar questions you would like answered, email her at ifixgrammar@charter.net