Pretense / Pretension
Pretense is to make believe; pretension is a claim
e.g. She makes no pretense to like her mother-in-law. (She does not pretend that she likes her mother-in-law)
e.g. He made no pretension to that award. (He never claimed that he received that award)
Ingenious / Ingenuous
Ingenious is clever; ingenuous is natural, free from deceit.
e.g. I must say that was an ingenious way to fund the project.
e.g. The Mayor's response to the questions from the reporter was sincere and ingenuous.
Providing that / Provided that
Providing that is incorrect; provided that means on condition that
e.g. You can go out to play provided (that) you have finished your homework. (meaning: on condition that)
e.g. You can keep the book for another week providing that no one has reserved it (incorrect: provided that should be used instead)
e.g. The millionaire has helped the poor, providing many of them with food and shelter. (correct; meaning: giving or offering)
Indoor / Indoors
Indoor is an adjective; indoors is an adverb.
e.g. Bowling is an indoor game.
e.g. It's going to rain; let's go indoors.
Terminable / Terminal
Terminable: can be ended; terminal: at the end.
e.g. Your job is only temporary and terminable at any time.
e.g. The doctor told the patient that she had terminal cancer.
Complacent / Complaisant / Compliant
Complacent means being self-satisfied; complaisant means being too eager to please; compliant means obeying or submissive
e.g. I was filled with a complacent satisfaction when I eventually completed the project.
e.g. You are too complaisant with your boss: you over flatter him.
e.g. Unlike the computer, people are not compliant, and neither are they predictable. Observable / Observant
Observable: can be seen or noticed; observant: quick to pay attention.
e.g. The solution to the problem is observable to many scientists.
e.g. To be a good scientist, you must be observant of all the relevant details and data.
Welcome / Welcomed
Welcome is an adjective or a verb; welcomed is a participle.
e.g. You are most welcome.
e.g. This is a welcome party for all newcomers.
e.g. I like to welcome all of you.
e.g. The guests were welcomed by all of us in front of the house.
Defuse: decrease the danger, such as deactivate a bomb; diffuse: spread over a wide area.
e.g. It is difficult to defuse the conflicts in the Middle East.
e.g. Once you open the bottle of fragrant herbs, their scents will diffuse.
Read / Peruse
Read: look at and understand; peruse: read thoroughly.
e.g. Don’t just read through the document; you have to peruse it to see if there is any hidden code.
Accountable to / Accountable for
Accountable to someone; accountable for something
(meaning "responsible for").
e.g. The CEO is accountable to the Board; he has to be accountable for all his business decisions.