Sorry if this sounds a bit harsh, but I'm puzzled by this reply. It's as if you stopped reading my comment immediately after the phrase "otherwise identical words distinguished from each other", and ignored the next part, which happened to be the most important part. So let me try again, using bold for emphasis:

"tone" refers to a phenomenon in certain languages (most famously Chinese) wherein otherwise identical words are distinguished from each other -- in isolation, nothing to do with their placement in a sentence -- by the contour of one's voice when pronouncing them

Did you actually read the Wikipedia article that you cited? Here's an example it gives from Chinese:

1. mā "mother"
2. má "hemp"
3. mǎ "horse"
4. mà "scold"
5. ma (an interrogative particle)

This should have made it clear that we're talking about a different phenomenon from anything that occurs in standard varieties of English. In Chinese, the intonation pattern of an individual word is actually lexical -- it's a fixed property of the word that applies even when the word is pronounced in isolation, entirely like the pattern of consonant and vowel sounds in the word. The five Chinese words above are not homophones, unlike "have" ("possess") and "have" (auxiliary) in English. The two senses of English "have" can't be distinguished when the word is pronounced by itself.