"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.

"CANVAS" and "CANVASS"

"Canvas" is a type of strong, heavy cloth. "Canvass" means to seek support or opinions, usually by going door to door. Ex.: The artist painted on a canvas. The politician will canvass the neighborhood for votes.