Common mistakes in English Usage: either is / either are, economic / economical, e.g. / i.e., free rein / free reign, flammable / inflammable, farther / further, good / better / best, good / well, historic / historical, incident / incidence.
Either, which may be either a pronoun or an adjective, is singular. Its modern meaning is "one or the other of two."
INCORRECT: Either Jack or Joan are correct.
CORRECT: Either Jack or Joan is correct.
When either introduces a choice between two things, the verb must be singular: Either the Honda or the Ford belongs to Harry. Either one of the books is a good choice.
Confusion arises when either introduces an either...or construction in which one of the choices is singular and one is plural. In such a case, the verb will agree with the nearer noun: Either hot dogs or pizza is on the menu for tonight. Either pizza or hot dogs are on the menu for tonight.
Neither, like either, is a singular word that usually takes a singular verb. In a neither...nor construction that contains a singular noun and a plural noun, the verb agrees with a plural noun that comes before it: Neither bad morals nor hypocrisy is wanted in a public official. Neither hypocrisy nor bad morals are wanted in a public official.
Economic refers to economics and the economy. Economical refers to getting the most value for one's money. The government must address serious economic problems. Families living on reduced means must make economical food choices.
INCORRECT: Eating at home is more economic than dining out.
CORRECT: Eating at home is more economical than dining out.
The abbreviation e.g. stands for the Latin expression exempli gratia and means "for example". The abbreviation i.e. stands for the Latin expression id est ("it is") and is used in English to mean "in other words." The farmer grows several kinds of soft fruit, e.g., strawberries, blueberries, and grapes.
INCORRECT: Boswell asked Dr. Johnson about every trivial detail, e.g., he made himself a daily nuisance.
CORRECT: Boswell asked Dr. Johnson about every trivial detail, i.e., he made himself a daily nuisance.
Free rein is a term that originated with riding. It refers to holding the horse's reins loosely, so as to permit the horse to move more freely. The figurative sense relates to any kind of unimpeded freedom. Reign refers to the authority of a monarch. Although commonly seen, "free reign" is incorrect.
INCORRECT: Unfortunately, their parents give them free reign on the weekends.
CORRECT: Unfortunately, their parents give them free rein on the weekends.
Both words, flammable and inflammable, mean "capable of bursting into flames." In modern usage the term inflammable is being dropped because the prefix -in, which means "into" in inflammable, is often confused with the prefix -in which means "not." The better practice is to use nonflammable as the opposite of flammable.
INCORRECT: These pajamas can't burn because they're inflammable.
CORRECT: These pajamas CAN burn because they're inflammable.
Farther is the comparative of the adjective far. It is used as an adverb to mean “to or at a more advanced point.” For example: He rode farther down the road. Some speakers argue a difference between the adverbial uses of farther and further. In general usage, however, the choice between farther and further is a matter of preference. He rode further down the road.
As a verb, further means “to help forward, to assist.” He would stop at nothing to further his ambition.
Good has the irregular comparative forms better and best. The word better is used to compare two people or things: This rope is better than that one. The word best used to compare three or more people or things: Charlie is the best player on the football team.
INCORRECT: Who's the best runner, Jack or Jill?
CORRECT: Who's the better runner, Jack or Jill?
Good is an adjective. Well is an adverb. When describing an action, the word to use is well. A great many English speakers cringe when they hear "I'm doing good" as the response to the polite question "How are you doing?" Writers aiming at standard usage acceptable to a wide audience will do well to avoid using good as an adverb.
INCORRECT: I hope I did good on the exam.
CORRECT: I hope did well on the exam.
Historical is an adjective that refers to anything that has happened in the past. Historic is an adjective to describe an event or invention that had or will have a major impact on future events. For example: The novel is based on historical events in the settling of the American West. The driving of the Golden Spike was a historic event.
INCORRECT: The signing of the bill today will be a historical event.
CORRECT: The signing of the bill today will be a historic event.
Incidence is a noun meaning "the extent of something's influence." Incident is a noun meaning "an occurrence or an event." For example: The incident involved a trailer truck and a Miata. What is the incidence of poverty among women?
INCORRECT: The witness described the incidence to the police.
CORRECT: The witness described the incident to the police.