Which best describes a homonym?

A homonym is best described as words that have the same spelling or sound but different meanings. This includes words that are both spelled and pronounced the same while having distinct definitions, such as "bat" (the flying mammal) and "bat" (the equipment used in baseball). Understanding this concept is essential for grasping the nuances of language, as homonyms can potentially lead to confusion in both spoken and written communication due to their similar sounds or spellings but vastly different meanings.

The other options do not accurately capture the definition of a homonym. Words that are spelled differently but sound the same refer to homophones, not homonyms. Synonyms are words that share similar meanings, which does not pertain to the concept of homonyms. Finally, the notion that words cannot be used in sentences is irrelevant to the definition of homonyms and does not contribute to the understanding of the term at all.