06/16/08 5 Pairs of Words Often Confused 1. "Principal" and "principle." "Principal" means head or chief (like of a company or school), while "principle" is a basic truth or tenet. 2. "Complement" and "compliment." Unless you're giving away free stuff or telling someone how nice she looks today, you probably mean the first one, which is defined as "to complete." 3. "Fewer" and "less." The supermarket checkouts should say "10 items or fewer" because "fewer" means a smaller number of units. "Less," on the other hand, means a smaller quantity. In other words, if you can't count it, use "less." 4. "Capitol" and "capital." "Capitol" refers to that building in Washington where the legislature meets, while "capital" relates to money or is an uppercase letter. 5. "Bi-monthly" and "semi-monthly." WHY magazine is published bi-monthly, or every two months. Semi-monthly means twice a month.   View WHY Xtra tips from previous weeks.