Recommended by Ero Hime
"WEATHER" and "WHETHER"
"Weather" refers to the atmospheric conditions. "Whether" is used to introduce alternatives or choices. Ex.: The weather is perfect for a picnic. I'm not sure whether to wear a jacket or not.
"ELICIT" and "ILLICIT"
"Elicit" means to draw out or provoke a response. "Illicit" means illegal or forbidden. Ex.: The teacher's question elicited a lively discussion. The police uncovered an illicit gambling operation.