Polysemy

Although closely related in meaning to homonym, lexicographers distinguish between polysemes, different uses of the same word, as walk the dog, take a walk, Lambeth Walk, going walking, which they define in a single dictionary entry, and homonyms like fluke, which have multiple meanings and different etymologies, and are therefore separate definitions.

There is clearly a gray area between the two ideas, but homonyms are much better known to average speakers, while polysemes are a matter for specialists.