a, an Use “a” before words with consonant sounds, such as “a tough competitor.” Use “an” before words with vowel sounds, such as “an opposing team” or “an honorable effort.”
accept, except Accept means to receive, e.g. “She accepted the offer from the university.” Except means to exclude, e.g. “He said he liked everything except the cafeteria food.”
affect, effect Affect, when used as a verb, means to influence, e.g “She said her mother’s opinion would not affect her own.” Affect can be used as a noun, but should generally be avoided. Effect, when used as a noun, means the outcome, e.g. “The effect was a winning season.” Effect can be used as a verb, but should generally be avoided.
ages Always use figures. Hyphenate the age when used as an adjective before a noun, e.g “The 15-year-old girl” but “the girl is 15 years old.”
among, between Among refers to more than two subjects, e.g. “The discussion was among Ben, John and Dan.” Between is used for two subjects, e.g. “The house is between Sixth and Seventh streets.”
because, since Because is used when one thing was caused by another, e.g. “She left because she had homework.” Since should be used as a time reference, e.g. “He hasn’t been back since he graduated.”
complement, compliment Complement means one thing pairs well with another, e.g. “Her dress complements her shoes.” To compliment is to praise, e.g. “He complimented his coach by saying he was the best role model he’s ever had.”
convince, persuade Convinced can be used with that or of, e.g. “She was convinced that UCLA was the right school for her.” You are persuaded to do something, e.g. “His father persuaded him to play baseball.”
different from Not different than.
either… or, neither… nor
farther, further Farther is used for physical distance, e.g. “She ran two miles farther today than she did yesterday.” Further is used for an extension of time or degree, e.g. “He further developed his pitching ability during the summer.”
fewer, less Fewer is used for individual items, e.g. “Fewer than 15 people make the cut.” Less is used for bulk items, e.g. “She had less money after her trip to the mall.”
good, well Good (adj.) means adequate or better than average. Good should not be used as an adverb. Well (adj.) means proper or healthy. Well (adv.) means skillfully.
hopefully Means in a hopeful manner, not “it is hoped.” Right: “The team hopes to win the championship.” Wrong: “The team will hopefully win the championship.”
it’s, its It’s is a contraction that can either mean “it is” or “it has.” Its is a possessive pronoun, e.g. “The football team lost its last game.”
literally In general, avoid using the term.
-ly Do not use a hyphen between adverbs ending in -ly and adjectives they modify, e.g. “a fully informed woman.” (AP Stylebook)
on Do not use on before a day or date of the week when its absence would not lead to confusion or it’s at the beginning of the sentence, e.g. “The game is Friday” and “On Friday, the school with close at noon.” Use on to avoid awkward juxtaposition of a date and name, e.g. “Smith will play Davis on Thursday.” (AP Stylebook)
over This should be used in reference to spatial relationships, e.g. “The bridge runs over the Missouri River.” More than should be used for numerals, e.g. “The club raised more than $500 for charity.”
principal, principle Principal is the main administrator. Principle is a fundamental truth or guiding belief.
that, which (pronouns) There are a few complicated rules for that and which, but the main point to know is that stands alone without a comma whereas which is always preceded by a comma. In some cases, the words can be used interchangeably with correct grammar. For example, “She went to the bookstore that is downtown” and “She went to the bookstore, which is downtown.”
their, there, they’re Their is a possessive pronoun, e.g. “It’s their business.” There is to describe a location, e.g. “They went there after the game.” There can also be used with the force of a pronoun when the real subject follows the verb, e.g. “There is nothing I can do about it.” They’re is a contraction for they are.
unique Only use if something is truly one of a kind.
who’s, whose Who’s is a contraction for who is. Whose is the possessive, e.g. “I asked whose wallet it was.”
who, whom Who is the pronoun used for people. It is the subject (not object) of the sentence, clause or phrase, e.g. “Who is going to the party?” Whom is used when someone is the object of a verb or preposition, e.g. “For whom are you calling?”