1、Misusing i.e. and e.g. Do not confuse these two. They do not mean the same thing!
i.e. = that is
e.g. = for example
(Many people think that ‘i.e’ stands for ‘in example.’ That is false. Both are abbreviations for two different latin phrases.)
2、Using ‘if’ when you should use ‘whether’.
Incorrect: I do not know if this is true.
Correct: I do not know whether this is true.
Correct: If this is true, then you are wrong.
3、Confusing ‘there’ with ‘their.’ ‘Their’ indicates possession, ‘there’ does not.
Incorrect: There problem was a lack of courage.
Correct: Their problem was a lack of courage.
Incorrect: Their are a lot of problems here.
Correct: There are a lot of problems here.
Incorrect: We should try and change the law.
Correct: We should try to change the law.
5、Letting your accent get in the way of things.
Incorrect: Mind and brain are one in the same thing.
Correct: Mind and brain are one and the same thing.
Incorrect: Socrates should of fought.
Correct: Socrates should have fought.
6、Improper form of the plural possessive of names.
Incorrect: Descarte’s problem was ….
Incorrect: Descartes problem was….
Correct: Descartes’ problem was….
Correct: Descartes’s problem was….
(Note: Either of the last two is acceptable only for names ending in ‘s’ like ‘Descartes’ or ‘Jesus.’ Otherwise, always go with the last example–i.e., add an apostrophe and an ‘s.’ The convention is usaully to not add an extra ‘s’ for old names, such as ‘Descartes’ and ‘Jesus.’ So, to say that this is the book that Rawls owns, people often write: “This is Rawls’s book.”)
7、Improper use of semi-colons.
Incorrect: The following will be on the test; Locke, Hume, Parfit.
Incorrect: Although there is no right answer; there are many wrong answers.
Correct: There is no right answer; there are many wrong answers.
(The Rule: Use a semi-colon only where you could use a period instead. In other words, a semi-colon must join two clauses that could stand by themselves as complete sentences. The semi-colin is just used to indicate that the two sentences are connected or intimately related.)
8、Confusing ‘then’ and ‘than’.
Incorrect: If this is true, than I’m a fool.
Incorrect: I am more of a fool then you are.
Correct: If this is true, then I’m a fool.
Correct: I am more of a fool than you are.
9、Its versus it’s.
Incorrect: Its easy to make this mistake.
Incorrect: It’s pages are crumbling.
Correct: It’s easy to make this mistake.
Correct: Its pages are crumbling.