Intrinsically memorable words have unique associations with their meanings.

What makes a word memorable? An important claim from past work is that words are encoded by their meanings and not their forms. If true, then, following rational analysis, memorable words should uniquely pick out a particular meaning, which means they should have few or no synonyms, and they should be unambiguous. Across two large-scale recognition-memory experiments (2,222 target words and > 600 participants each, plus 3,780 participants for the norming experiments), we found that memory performance is overall high, and some words are consistently remembered better than others. Critically, the most memorable words indeed have a one-to-one relationship with their meanings-with number of synonyms being a stronger contributor than number of meanings-and number of synonyms outperforms other predictors (such as imageability, frequency, or contextual diversity) of memorability that have been proposed in the past. (PsycInfo Database Record (c) 2025 APA, all rights reserved).