beside, besides Beside means "at the side of." Besides means "in addition to." (Secret Service agents stand beside the President. There are other motives besides greed.)
can't hardly A confusion between cannot and can hardly. The construction is unacceptable in formal writing. Sue cannot, can't or can hardly.
capital, capitol Capitol is the spelling used for the government building ("We could see the capitol from our hotel building"), while capital is the correct spelling for all other uses ("What is the capital of Colorado?").
choose, chose Choose is a present tense verb ("Choose your partners"), while chose is a past tense verb ("The girls chose two seniors").
cite, site, sight Cite means to indicate ("You must cite all sources used in your paper"). A site is a place ("Independence is the site of Harry Truman's home"). A sight is a vision ("You're a sight for sore eyes!").
coarse, course Coarse is an adjective meaning rough or crude ("He uses coarse language"), while course is a noun meaning a path of action ("The course in speech helped my diction").
complement, compliment Complement means to make whole or complete or that which makes whole or complete ("The complement, or full crew, is 600 people). Compliment means respect, affection, or esteem ("Convey my compliments to the captain").
consul, council, councilor, counsel, counselor Consul is a diplomat to a foreign country. Council refers to a group to discuss and take action on official matters ("Student Council"); a councilor is a member of such a group. Counsel is advice or to advise. A counselor ("your guidance counselor") is an adviser.
des' ert, desert', dessert A desert (pronounced des' ert) is a dry region. To desert (pronounced desert') is to leave. The dessert is the last part a meal ("We ate chocolate cake for dessert).
different from, different than Although both different from and different than are common American usages, the preferred idiom is different from.
emigrant, immigrant An emigrant is a person who moves out of a country; an immigrant is one who moves into a country. Thus, refugees from Central America and elsewhere who settle in the United States are emigrants from their native countries and immigrants here. A similar distinction holds for the verbs emigrate and immigrate.
fewer, less Fewer is used to describe things that can be counted. Less refers to quantity or degree. (Patrick has fewer headaches than he used to have. There has been less rain this year than last year. This dishwasher will give you less trouble than that one.)
formally, formerly Formally means in a formal or standardized manner ("for weddings one should dress formally"). Formerly means previously ("The high ridges of the Blue Ridge Mountains were formerly the bed of an ancient sea").
further, farther; furthest, farthest Generally, in good usage, farther is used for comparisons of distance and further for anything else. (Robin's punt went farther than Jenny's. [distance] Pablo has advanced further in his study of English. [extent])
good, well Good is an adjective. Do not use it to modify a verb. Well is an adverb except in three uses: (1) when used to mean "healthy," (2) when used to mean "neatly groomed" or "attractively dressed," and (3) when used to mean "satisfactory."
had of, off of The use of is both unnecessary and undesirable.
Nonstandard: If you had of played, we would have won.
Standard: If you had played, we would have won.
Nonstandard: The box fell off of the shelf.
Standard: The box fell off the shelf.