The context includes such things as the ideas conveyed by adjacent words and nearby phrases, the known or probable purpose and register of the conversation or document, and the orientation (time and place) implied or expressed.
A word sense corresponds either neatly to a seme (the smallest possible unit of meaning) or a sememe (larger unit of meaning), and polysemy of a word of phrase is the property of having multiple semes or sememes and thus multiple senses.
Examples are the variation in senses of the term "wood wool" and in those of the word "bean".
This pattern entails that natural language can often lack explicitness about hyponymy and hypernymy.
Broad medical terms usually followed by qualifiers, such as those in relation to certain conditions or types of anatomical locations are polysemic, and older conceptual words are with few exceptions highly polysemic (and usually beyond shades of similar meaning into the realms of being ambiguous).