Avoid the following common mistakes:

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• to affect vs. to effect: This is a terribly common mistake. The verb 'to effect' is very formal and rarely used; it means 'to succeed in causing something planned to happen.' When students use 'to effect,' they almost always have a meaning in mind that is captured by the verb 'to affect': "The presence of other people affects an individual's performance." "She was strongly affected by her recent life events." The error comes from the fact that 'to effect' is synonymous with the phrase 'something has an effect on something else.' So don't use the verb 'to effect'---use 'to affect' or 'to have an effect.'

• Genitive ['s]: "My mother's [not mothers] decision was difficult."

• Its vs. It's: For example, "Its [not It's] most attractive feature is the price"

• Gender-neutral language: To avoid the traditional sexist use of "he," use one or more of the following strategies: (a) alternate references to male and female (e.g., if you gave one example about a woman in one paragraph, use an example about a man in the next paragraph); (a) say "his or her" and "he or she" (but don't use the clumsy his/her or s/he); (c) use the plural form "people" (but don't say "they" if you refer to a single person).

• tenet vs. tenant: A tenet of a theory is a major principle on which the theory is based. Your tenant pays rent to you every month.

• A colon [:] introduces a closely related sentence part (e.g., "He made one major mistake: not to calculate the probabilities right"). The part after the colon can be a complete or an incomplete sentence.
  A semicolon [;] separates two sentence parts more distinctly than a comma does and less distinctly than a period ("She was not tired; he was exhausted"). The part after the semicolon must be a complete sentence.

• Plural words: "Phenomena" is a plural world--its singular form is "phenomenon" ("These phenomena are intriguing"). The same holds for "data," which is the plural of "datum" ("The data do not confirm the hypothesis") and "criteria," which is the plural of "criterion" ("The criteria were set too high").