Common English mistakes in spelling, punctuation, and usage

1. Accept: verb meaning "to receive with approval", as in "The compiler won't accept that statement."
2. Except: preposition meaning "other than" and verb meaning "to exclude", as in "Spelling any language is easy, except English."

1. An: Indefinite article, used instead of "a" when placed before a word starting with a vowel
2. And: Conjunction
   

1. Are: Plural conjugation of the verb "to be," as in "Motorcycles are cool."
2. Our: Plural first-person possessive, as in "Our car just blew up."

1. Affect: verb meaning "to influence", as in "His statement affected my boss's opinion of my work."
2. Effect: noun meaning "influence" or "consequence", as in "His statement's effect was that I got fired."
3. Effect: verb meaning "to bring about", as in "They effected my termination immediately."
4. Impact: verb meaning "to collide", or noun meaning "collision".  Often incorrectly replaces "affect" and "effect" for people who can't remember the difference, such as Minnesota Public Radio's host of their Midmorning call-in show for deeply confused people.
   

1. Assert: verb meaning "to claim the truth of a proposition", or in digital design "to emit a 1."
2. Exert: verb meaning "to expend energy."

1. Assure: verb meaning "to guarantee (a truth or success)"
2. Ensure: verb meaning "to make certain"
3. Insure: verb meaning "to underwrite compensation for particular risks"
   

1. Breath: noun meaning "pull air into lungs and push it back out."
2. Breathe: verb meaning "to take breaths."

1. Bi: prefix meaning "two"
   
2. Buy: verb meaning "to acquire in exchange for money", noun meaning an act of same
3. By: preposition meaning "near" or "through the means of"
4. Bye: noun meaning "right to advance in a tournament without competing"; also contraction of "goodbye", which itself is a contraction of "God by ye".
   

1. Capital: biggest, most important, largest, as in "CAPITAL letters"
2. Capitol: building with a dome and legislators
   

1. Do: verb meaning "to act"
2. Due: conjunction, with "to"; also noun meaning "that which is owed"
   

1. e.g.: Abbreviation of "for example", as in "I get way too much spam, e.g. about home mortgages." (exemplia gratia)
2. i.e.: Abbreviation of "that is to say", as in "The boss distributed a paperless communication to his resources; i.e., he sent e-mail." (id est)

1. These letters are often transposed.  A good rule for English is "I before E except after C, but WEIRD is weird."

1. Farther: Of a greater distance
2. Further: More advanced
   

1. Foreword: noun meaning "word(s) before," similar to "preface."
2. Forward: noun meaning "the direction in front of you, unless you've twisted your neck painfully."

1. Not really a word, but commonly used to mean "software capability" or "feature" or "thing I don't understand."
   

1. Here: noun meaning "not over there."
2. Hear: verb meaning "sense with the ears", also agreement in "Hear (him), hear (him)!"

1. Hypocracy: not a word, unless there's a noun meaning "government by hypocrites," maybe.
2. Hypocrisy: noun meaning "saying one thing and doing another." 

1. Not a word.  Often used in place of "significant" or "consequential" or "noteworthy."
   

1. It's: contraction of "it is", as in "Slashdot is informative but it's often annoying."
2. Its: possessive of "it", as in "Slashdot is informative but its editors can't spell."

1. Loose: adjective meaning "not tight."
2. Lose: verb meaning "not to win" or "to possess no longer."
   

1. A pompous noun often meaning "person" in contexts where said person is being mistreated as an interchangeable part by a bad manager.  "It would take at least two resources to implement that functionality, and that would be impactive on the schedule." ( I work with people who really talk like this all the time without shame, thinking that it makes them sound important instead of pathetically retarded.)
   

1. Populace: noun meaning "the population."
2. Populous: adjective meaning "populated."

1. Principal: adjective meaning "primary", noun meaning "head teacher in a school."
   
2. Principle: noun meaning "rule", as in "The conservation of energy principle."

1. 'S: Regular singular possessive ending, as in "Fred's car." But no apostrophe is used in "its", as in "My computer crashed its hard disk."  Sometimes a mere apostrophe suffices after nouns ending in S, as in "Jesus' new bicycle", but that's optional.
2. 'S: Contraction of "is", as in "it's" for "it is."
   
3. S': Regular plural possessive ending, as in "There are often problems in Slashdot writers' punctuation."
   
4. S: Regular first person singular verb conjugation ending, as in "He gets it".  Never ever has an apostrophe!
5. S: Regulal plural ending, as in "cats and dogs".  Never has an apostrophe, not even for plural acronyms as in "Overpriced Microsoft OSs".
   

1. Scalar: noun meaning "quantity not a vector."
2. Scaler: noun meaning "one who scales," I suppose.  Probably appropriate only in discussions of fish-cleaning or metrology.

1. Than: comparative preposition, as in "Kuro5hin has better spellers than Slashdot."
2. Then: noun meaning "at that time."
   

1. Their: possessive of "they."
2. There: noun meaning "not here."
3. They're: contraction of "they are."

1. To: preposition meaning "in the direction of" and particle used to form verb infinitives, as in "to form verb infinitives."
2. Too: adjectival modifier meaning "excessively."
3. Two: integer value equal to the sum of unity with itself, also denoted 2 in so-called Arabic numerals and II in Roman times.
   

1. Wear: verb meaning "to bear upon the body as clothing" or "to abrade", or a collective noun meaning "clothing."
2. Where: preposition and question word, as in "Where did my coffee mug go?  Where they all go, I suppose."

1. Who's: Contraction of "who is", as in "Who's on first?"
2. Whose: Question word, as in "Whose dog ate my petunias?", and relative pronoun, as in "This is my neighbor Clyde, whose dog ate my petunias."
   

1. Your: possessive of "you."
2. You're: contraction of "you are."