1. An abridgement of Bill Bryson’s “A Dictionary of Troublesome Words.”

2. Affect/Effect:
Affect as verb: to influence. "Smoking may affect your health."
Affect as noun: to adopt a pose or manner. "She affected ignorance."

3. Effect as verb: to accomplish, to bring about
Effect as verb: to accomplish, to bring about. "The prisoners effected an escape."
Effect as noun: something brought about by a change or cause. "The damaging effects of war."
(also means property, as in "personal effects)

4. In common use: affect is more often used as a verb, effect is more often used as a noun.

5. all right vs. alright All right is the correct use.
Two separate words.

6. basically
Basically, leave it out

7. besides Means also or in addition to, not alternatively.
Incorrect: "The wound must have been made by something besides the handle of the gear lever."
Correct: "The wound must have been made by something other than the handle of the gear lever."
Correct use of besides: "Besides the Greeks, the Romans also fought over the island of Sicily."

8. can vs. may Possible vs. permissible.
You can drive your car on the wrong side of the street, but you may not.

9. close proximity Inescapably tautological. Use "near" or "close to."
Incorrect: "The knife was in close proximity to the spoon."
Correct: "The knife was close to the spoon."

10. collision Used to describe two moving objects coming together.
Not for a moving object and a stationary one.
A car does not collide with a tree.

11. comparatively Only to be used when making comparisons.
Incorrect: "Comparatively little progress was made in the talks yesterday."
Compared to what?

12. compliment vs. complement
Compliment: to praise. "I complimented her attire."
Complement: to fill out or make whole. "Roses in the silver bowl complemented the table."

13. conceived Refers to a single event.
Incorrect: "Last week, twenty-five years after it was first conceived..."
Correct: "Last week, twenty-five years after it was conceived."
Also, be wary of "initially conceived" and "originally conceived."

14. couldn't of Should be “couldn't have.”
Comes from an often-spoken double contraction: couldn't've

15. current, currently: For contrasting the present with the past.
Unnecessary in phrases like "Oil prices are currently $44 a barrel."
Why not just "Oil prices are $44 a barrel?"

16. cut back "We had to cut back wheat production."
Do you need the "back" here?

17. decimate Literally, to reduce by a tenth. Maybe.
Should not be used to denote total destruction.

18. diagnosis vs. prognosis
diagnosis: to identify and define a problem.
prognosis: A projection of the course and likely outcome of a problem.

19. different
Sometimes unecessary: "Shakespeare wrote thirty-seven different plays."

20. Dilemma
Applies when someone is faced with two distinct courses of action, of which neither is clearly superior.
Does not refer to just any difficulty or predicament.

21. discrete vs. discreet Discreet: careful, showing good judgement.
Discrete: singular, unattached, unrelated.

22. dos and don'ts
Note the apostrophe.
And the lack thereof.

23. Each When each is the subject of a sentence, it is singular.
"Each of the pens was red."
When each modifies a plural subject, the subject is still plural.
"Drivers licenses each have unique identification numbers."

24. Simple rule to decide on the subject:
If each precedes the verb, subsequent nouns and pronouns are plural:
"They each are subject to sentences of five years"

25. If each follows the verb, subsequent nouns and pronouns are singular:
"They are each subject to a sentence of five years."

26. Equally as Always wrong. Incorrect: "This is equally as good."
Correct: "This is as good." Or "This is equally good."

27. exception proves the rule
In modern English, a bewildering statement.
Comes from the use of "proof" meaning to prove or to test.

28. fewer vs less Fewer: refers to discrete numbers.
Less: refers to quantities.
Fewer people.
Less water.

29. gender vs. sex
Gender: originally only used in a grammatical context, became a euphemism for sex in the nineteenth century.
Later disdained as old-fashioned and overdelicate.
Now used as a fine distinction in feminist theory and transgender politics.

30. indexes vs. indices Which is the plural of index?
Either is acceptable!

31. irregardless
Stop using this word!

32. last vs. latest
When referring to a temporal event, both can mean most recent.
When there's confusion, though, use appropriate word.

33. The most recent, but not final, episode of a television series
The most recent, but not final, episode of a television series? It's the latest episode of the series.
The series finale of "Buffy the Vampire Slayer"? It's the last episode of the series.

34. most Often incorrectly used in speech to replace "almost".
Incorrect: "Thai cuisine uses fish sauce to flavor most everything."

35. percentage, fraction:
"This drug has proven useful in a percentage of cases."
"Teenage pregnancy rates have dropped to a fraction of what they once were."
Has it proven useful in 1% of cases?
Have teenage pregnancy rates dropped to 999/1000ths of what they once were?

36. plan ahead:
Another tautology.
Would you plan behind?

37. precautionary measure
Can nearly always be shortened to precaution.

38. quantum leap
The scientific sense is of a movement or advance that is discrete and measurable, but not necessarily, or even usually, dramatic.

39. situation Can be useful as a noun:
"We advised the president of the situation." Or
"The situation was delicate."

40. Usually unnecessary as an adjective:
"We hoped to contain the crisis situation."

41. strata, stratum A single layer is a stratum.
Strata signifies more than one.

42. That vs. which Used in restrictive or nonrestrictive clauses.
Non-restrictive: (you want to describe a tree, and whether it has leaves or not is incidental): "The tree, which had no leaves, was a birch.”
(The sentence could read coherently without the center clause. )

43. Restrictive: (you want to identify which of several trees is a birch)
"The tree that had no leaves was a birch.”
(Refers to a specific tree, does not mean the same thing without the "that" clause.)

44. toward vs. towards: Both are grammatically correct.
Toward is preferred in American English.
Towards is preferred in British English.