Many words are associated with more than a single meaning. Words are sometimes "ambiguous," applying to unrelated meanings, but the majority of frequent words are "polysemous" in that they apply to multiple "related" meanings. In a preregistered design that included 2 tasks, we tested adults' and 4.5- to 7-year-old children's ability to learn 4 novel polysemous words or 4 novel ambiguous words. Both children and adults demonstrated a polysemy over ambiguity learning advantage on each task after exposure, showing better learning of novel words with multiple related meanings than novel words with unrelated meanings. Stimuli in the polysemy condition were designed and then normed to guard against learners relying on a simple definition to distinguish the multiple target meanings for each word from foils. We retested available participants after a week-long delay without providing additional exposure and found that adults' performance remained strong in the polysemy condition in 1 task, and children's performance remained strong in the polysemy condition in both tasks. We conclude that participants are adept at learning polysemous words that vary along multiple dimensions. Current results are consistent with the idea that ambiguous meanings of a word compete, but polysemous meanings instead reinforce one another.