This study investigates how the brain represents polysemy, the phenomenon where a single word has multiple related meanings. Using magnetoencephalography (MEG), the researchers examined whether different senses of a word are stored as separate lexical entries or share a common representation. The study compared polysemy with homonymy and semantic relatedness, using a priming paradigm to assess how different senses of a word affect lexical activation. The results showed that polysemy effects are distinct from similarity effects. In the left hemisphere, sense-relatedness elicited shorter latencies of the M350 source, which is associated with lexical activation. In the right hemisphere, sense-related targets peaked later than unrelated targets, suggesting competition between related senses. These findings support the idea that polysemy involves both representational identity and difference: related senses connect to the same abstract lexical representation but are distinctly listed within that representation. The study also found that polysemy effects are "special" and cannot be explained solely by sound and meaning relatedness. Instead, they can be explained by the hypothesis that related senses share a morphological root. This was evidenced by left hemisphere M350 priming, indicating that different senses of the same word activate the same morphological root. The results suggest that the mental lexicon represents polysemy with a shared morphological root, rather than as separate lexical entries. This has important implications for understanding how the brain processes language and how different meanings of words are represented. The study highlights the importance of using fine-grained measures like MEG to investigate how different forms of ambiguity are represented in the brain.This study investigates how the brain represents polysemy, the phenomenon where a single word has multiple related meanings. Using magnetoencephalography (MEG), the researchers examined whether different senses of a word are stored as separate lexical entries or share a common representation. The study compared polysemy with homonymy and semantic relatedness, using a priming paradigm to assess how different senses of a word affect lexical activation. The results showed that polysemy effects are distinct from similarity effects. In the left hemisphere, sense-relatedness elicited shorter latencies of the M350 source, which is associated with lexical activation. In the right hemisphere, sense-related targets peaked later than unrelated targets, suggesting competition between related senses. These findings support the idea that polysemy involves both representational identity and difference: related senses connect to the same abstract lexical representation but are distinctly listed within that representation. The study also found that polysemy effects are "special" and cannot be explained solely by sound and meaning relatedness. Instead, they can be explained by the hypothesis that related senses share a morphological root. This was evidenced by left hemisphere M350 priming, indicating that different senses of the same word activate the same morphological root. The results suggest that the mental lexicon represents polysemy with a shared morphological root, rather than as separate lexical entries. This has important implications for understanding how the brain processes language and how different meanings of words are represented. The study highlights the importance of using fine-grained measures like MEG to investigate how different forms of ambiguity are represented in the brain.