Note: AHD4 = American Heritage Dictionary, fourth edition.

• Aggravate - some claim that this word can't be used in the sense of "to annoy" and "to oppress"
  • Disputed usage: It's the endless wait for luggage that aggravates me the most about air travel.
  • Undisputed usage: Being hit on the head by a falling brick aggravated my already painful headache.

• Ain't - though this word is widely used, it is normally viewed as non-standard. See ain't.

• Alibi - critics argue this cannot be used in the non-legal sense of "an explanation or excuse to avoid blame or justify action." Also, use of the word alibi as a verb is unacceptable to a large majority of AHD4's Usage Panel.

• Also - some contend this word should not be used to begin a sentence. AHD4 says "63 percent of the Usage Panel found acceptable the example The warranty covers all power-train components. Also, participating dealers back their work with a free lifetime service guarantee."

• Alternative - some hold that alternative should be used only when the number of choices involved is exactly two.

• A.m./p.m. - these are Latin abbreviations for ante merediem ("before noon") and post merediem ("after noon"), adverbial phrases. Some would argue that they therefore should not be used in English as nouns meaning "morning" and "afternoon".

• Amount - should not be substituted for number. If the thing referred to is countable, use number. If it is uncountable, use amount. (see less)
  • Disputed usage: I was amazed by the amount of people who visited my website.
  • Undisputed usage: The number of people in the lift must not exceed 10.
  • Undisputed usage: I was unimpressed by the amount of water consumed by the elephant.

• And - many feel that a sentence should never begin with the word "and". And on the other hand, some insist on using it that way, even though they are aware of the fact that others are peeved by such usage. Many Biblical verses begin with "and", as does William Blake's poem And did those feet in ancient time (aka Jerusalem). Fowler's Modern English Usage defends this use of "and".

• But - if and should not be used to begin sentences, then neither should but. These words are both conjunctions, so some traditionalists believe that they should be used only to link clauses within a sentence.

• Can - in spoken English, use of can to request or give permission, as in After you do your homework, you can go watch TV, is very common. However, in more formal usage many insist upon the distinction between may and can.

• Casket - its use as a synonym for coffin is sometimes condemned as a euphemism.

• Deprecate - the original meaning in English is deplore or express disapproval of (the Latin from which the word derives means "pray to avert evil", suggesting that some event would be a calamity). The word is now also used to mean play down, belittle or devalue, a shift that some language purists disapprove of, as it suggests the word is being confused with the similar word depreciate. Its use with the approximate meaning to declare obsolete in computer jargon is also sometimes deprecated.

• Fortuitously - is used by some interchangeably with fortunately, whereas, strictly speaking, fortuitousness is merely a reference to an occurrence depending on chance.

• Gender - is often used as a euphemism for sex.
  • Gender properly refers to grammatical gender, a feature in the grammar of a number of different languages. Some usage commentators believe that its use as a euphemism for sex is to be avoided as a genteelism.
  • Others note that some writers use sex and gender in different but related senses, using sex to refer to biological characteristics and gender to refer to social roles and expectations based on sex. Those who use gender in this fashion frequently take a controversially expansive view of the effects of social expectations on sex roles, and diminish the role of biology to purely physical characteristics. Those who use gender as a euphemism for sex may confuse readers who draw this distinction, or mislead readers by giving the impression that the writer has assumed or endorsed these beliefs. See gender identity, gender role

• Hoi polloi - There are two main usage issues regarding hoi polloi:
  • This Greek phrase meaning "the common people" has occasionally been used to mean "the aristocracy", perhaps because it sounds like hoity-toity or it looks somewhat like high and mighty. However, this definition is not accepted by any major dictionary, and indeed AHD4 says "Hoi polloi is sometimes incorrectly used to mean 'the elite'".
  • The other question surrounding hoi polloi is whether or not it is appropriate to use the article the preceding the phrase. The question arises because hoi is the Greek word for "the" in the phrase and classical purists complain that adding the makes the phrase a redundant "the the common people". Foreign phrases borrowed into English are often reanalyzed as single grammatical units, requiring an English article in appropriate contexts. AHD4 says "The Arabic element al- means "the", and appears in English nouns such as alcohol and alchemy. Thus, since no one would consider a phrase such as the alcohol to be redundant, criticizing the hoi polloi on similar grounds seems pedantic."

• Hopefully - some claim this word should not be used as an expression of confidence in an outcome.
  • Disputed usage: Hopefully I'll get that scholarship!
  • Undisputed usage: He was hopefully anticipating the upcoming film.

• Less - should not be substituted for fewer. If the thing referred to is countable, use fewer. If it is uncountable, use less.
  • Disputed usage: This lane 12 items or less.
  • Undisputed usage: We had fewer players on the team this season.
  • Undisputed usage: There is less water in the tank now.

• Literally - some writers say literally should not be used as a mere emphatic, unless the thing to which it refers is actually true. It is used to disambiguate a possible metaphorical interpretation of a phrase.
  • Undisputed usage: He literally painted the town red; he was the council painter and decorator.
  • Disputed usage: The party literally went with a bang. (No it didn't, unless there was an actual explosion).

• Not - according to some should not ever conclude a sentence. Others note that such usage is old enough and has been utilized by many of the best writers in the English language.

• Presently - traditionally means "after a short period of time." Recently, has been increasingly used as a synonym for "currently" or "at the present time."
  • Disputed usage: I am presently reading Wikipedia.
  • Undisputed usage: I will be finished with that activity presently.

• Refute - the traditional meaning is "disprove" or "dispel with reasoned arguments". It is now often used a mere synonym for "deny".

• Unique is often overused. It should be used when there is only one of something. A thing cannot be 'more unique' than something else.

• Who - prescriptive gammarians generally agree that "who" should be used only as a subject pronoun, the corresponding object pronoun being "whom". However, in colloquial speech, especially in the US, it is rather routinely used as an object unless it is immediately preceded by a preposition. Interestingly, almost no native speaker would fail to make the corresponding distinction between "he" and "him", or "she" and "her".
  • Undisputed usage: Who is talking to you?
  • Disputed usage: Who are you talking to?
  • Undisputed usage: To whom are you talking?
  • Incorrect usage: To who are you talking?
  • Dubious usage: Whom are you talking to?