What is the name for two words with opposite meanings?

Which sentence uses "they're," "their," and "there" correctly?

Which sentence is properly capitalized?

Which sentence uses "too" correctly?

Britney Spears is going to keep on dancing...

What is an artist's board used for mixing paints called?

Which work is likely not to be in the public domain in the United States?

Which is the term for the page on the left side in an open book?

Which spelled-out number is NOT hyphenated correctly?

Which means "to deny under oath"?

What type of error does this sentence have? "They walked along the Rio Grande River."