Etc should be abbreviated Et.C. or E.C. (et cetera)
A common expression is "centered around" but the more logical form would be "revolved around." Likewise: "honing in" for "homing in" and "mitigate against" for "militate against."
Can you be "off of" something or should it just be "off?"
Some might say that unique should not be thought of as a range, however, "somewhat unique" is a common expression.
Did you know that "graffito" is the singular form of "graffiti?" More common singular and plural forms from the Latin are: "bacterium-bacteria" (modern English has a plural of the Latin plural: "bacterias"); "cactus-cacti" (cactuses is common); "criterium-criteria;" "datum-data;" "grocery-groceries;" "kudo-kudos;" "medium-media;" "memorandum-memoranda" ("memo-memos"); "phenomenon-phenomena;" "specie-species;" stratum-strata."
"Liable" means "obligated" but it is commonly used to mean "likely" (synonym for "apt").
Can you be "between" more than two things? (or should you then use "among") "Switzerland is between France, Germany, and Italy." Another example like this is "each other" vs. "one another."
"Should" is the past tense of "shall" but today it usually has an auxiliary function: "You should go."
"Alot" is a nonword for "a lot." (credit for this one goes to my 11th grade English teacher)
"Hemeralopia" should not mean "night blindness." Medically used to mean reduced visual capacity in bright light.
"Holland" is really "The Netherlands" (Holland is the historic name; North and South Holland are provinces in The Netherlands)
Scholars once referred to wealthy snobs as the "hoi polloi" and the phrase has been incorrectly defined as "upper crust."