Genius vs. Ingenious vs. IngenuousHow to use "genius," "ingenious," and "ingenuous" correctly
Genius should only be used as a noun, not as an adjective:
Ingenius is an adjective. Someone ingenious is clever, and something ingenious is characterized by cleverness or resourcefulness. The noun form of ingenious is ingenuity.
a plan that shows great ingenuity
Someone ingenuous (also an adjective) is innocent, simple, candid, sincere, naive—sometimes to the point of lacking cunning or sophistication. The noun form of ingenuous is ingenuousness, and its antonym is disingenuous.
ingenuous child who couldn’t conceive of lying
seemed ingenuous, but was actually sly
the child’s disarming ingenuousness
a disingenuous explanation that was intended to be misleading
Be sure to spell these words correctly—remember the o in ingenious.
Common Errors in English Usage: Errors in diction and idiom commonly made by native speakers of English
List of Common Errors in English Usage (PDF): Printable version of the complete list
Common Grammar Errors: A list of common errors in grammar (topics like subject-verb agreement and parallelism) as distinct from usage