Period

We are all taught at a young age the importance of the period, and it's rare that an experiences writer will omit this very important terminal mark. However, did you know that there are 4 rules of period use? If you weren't aware of this interesting fact, don't fret; you probably already know them.

1. Use a period at the end of a complete sentence.

    Airplane travel has become commonplace in our hectic society.

    After finishing high school, Nicole will consider attending college.

2. Use periods (decimal points) with money and percentages.

    My allowance was $3.00 a week when I was thirteen years old.

    It's amazing that 34.7% of tenth graders who took the HSGQE failed to pass.

3. Use periods after initials.

    My favorite football player is L.C. Greenwood.

4. Use periods in some abbreviations.

Most uppercase and lowercase abbreviations still use a period.

    Months: Jan., Oct.

    Days: Mon., Wed.

    Titles: Gov., Sen., Rep., Mr., Mrs., Ms., M.D., Ph.D.

    Addresses: Ave., St., Rd., Blvd.

    Measurements: lb., oz., hr., min., ft., in., qt.

    Countries: U.S., U.K.

When all letters are capital letters, periods are usually not used.

    Agencies, companies, and organizations: CIA, NFL, FBI, IRS, NATO, YMCA

    Computer terms: RAM, CD/ROM

    Tests: PSAT, IQ, SAT, ACT, HSGQE

    Radio and television stations: WULF, KGOT, KABC, KUAC

    Medical terms: AIDS, PMS, SIDS

    Directions: SW, NE, NNW

Some miscellaneous abbreviations that don't use periods:

    UFO, DST. mph, rpm, kg, mg, Hz, Ca.

Go to The Guide to Grammar and Writing section on Periods.

Return back to Grammar Rules page.