"Demon" Word Pairs

Affect = To influence or have an effect on (almost always a verb).: The legislators' cooperation effected a major change in tax law.; The new code will affect individual taxpayers but will have no effect on businesses.

All ready = Completely prepared.
Already = By now or before now.: We were all ready to go to the movie, but it had already started.

Allusion = Indirect reference.
Illusion = Deceptive appearance.: His constant allusions to Shakespeare created the illusion that he was an intellectual.

Among = Shows a relationship involving three or more countable things (plural nouns).
Between = Shows a relationship involving two or more things, or a comparison of one thing to a group to which it belongs.: The four of us decided among ourselves that the choice was between St. Louis and Indianapolis.
Among = In the midst of countable things (plural nouns).: The firemen walked among the burning houses.
Amid, amidst, in = In the midst of uncountable things (singular nouns).: The firemen walked amid the wreckage.
Amount = Refers to uncountable items (singular nouns); denotes quantity, not number.
Number = Refers to countable things (plural nouns).: The amount of ice we can save depends on the number of containers available.
Better/Worse = Makes a comparison between two things.
Best/Worst = Makes a comparison among three or more things.: (This rule also extends to most other "EST" and "ST" superlatives: older/oldest; stronger/strongest; more/most; less/least; etc.)

Capital = Money, or a seat of government (Mnemonic: "ALbany is the capitAL of New York.")
Capitol = The building where Congress or other governing body meets.

Cite = Refer to, point out or formally charge.
Site = A place or location.: The committee will cite three examples of unfair labor practices at the job site.
Due to = means "caused by". It is usually correct only after a form of the verb "to be".: The school closings were due to the blizzard.
Due to the fact that = a wordy, wasteful construction. Always substitute because.
Because of = use instead of "due to" if the words "caused by" cannot be substituted:: The schools closed because of the blizzard.; Because of the blizzard, the schools closed.
Further = Additional time or amount.: I have no further interest in this subject.
Farther = Additional distance.: How much farther is it to Chicago?

Fewer = Refers to individual, countable items (plural nouns).
Less = Refers to general amounts (singular nouns).: This brand is less fattening because it has fewer calories.

Hopefully = An adverb meaning "in a hopeful manner" (rarely used).
I hope/It is hoped that = should be used instead of "hopefully".: The students are hopefully taking their final exams. I hope they pass.

Its = The possessive of it. All other nouns use 's to construct a possessive.
It's = Always a contraction for "it is".

Lie = Denotes a condition (the action is confined to the subject). Past tense is lay; present is lying; past participle is lain.: The Azores lie in the Atlantic.; He lay in pain waiting for help; he had lain there for hours.
Lay = Denotes an action from a subject to an object. Past tense is laid.: He was lying in bed while his wife laid out clothes for their trip.
Lied = Told a falsehood (past tense of lie).: He lied about where he laid the maps.
Over = Refers to general amounts or unspecified increments (i.e., references to money).
More than = Refers to individual, countable items.: Over half of our inventory is unsold, resulting in a loss of over three million dollars.; More than 100 complaints have been filed.

Principal (noun) = Means chief official or, in finance, capital sum. (Mnemonic: "Your principal is a prince of a pal.")
Principal (adjective) = Means foremost or major.
Principle = Always a noun meaning rule or axiom.

Sometime = at a point in time.: The law was passed sometime last year.
Some time = an adjective modifying time, producing the equivalent of a length of time.: The new policies have been in effect for some time now.
Stationary = Immobile, standing in place.
Stationery = Writing paper. (Mnemonic: "StationERy = papER.")

To = Always a preposition or part of a verb infinitive.: His goal was to climb to the top.
Too = An adverb meaning also or excessively.: It costs too much for me to go, too.

Who's = Always a contraction for who is.: Who's at the door?
Whose = The possessive of who.: Whose report is missing?

Who = Used when the reference is to the subject of the sentence (the noun that is carrying out the action of the verb).: Who mailed the bills? I don't remember who called.
Whom = Used when the reference is to the object of the sentence (the noun that the verb acts upon).: Whom should I ask? Tom Smith, whom Joe blamed for the problem, resigned today.