My definition of heteronym (previous posting) is from the OED, the complete edition of a few years back (I wish I could afford a new one). Heteronym is defined in the Merriam Webster Collegiate as "one of two or more homographs (as in a bass voice and bass, a fish) that differ in pronounciation and meaning." Mr. Red, the Merriam Webster Collegiate (there are poor imitations also labeled Webster) is the best dictionary for North Americans. If you are in the "mother country" the OED concise is still the best. Both are abridgements and leave out much including the history of the words, but they are portable and affordable. The OED is on line, but the subscription cost is prohibitive except for businesses. Canadians have a problem, since their usage is a mixture of OED and Webster usages plus Franglais. So-called Canadian edition dictionaries are p--- poor.