Human communication relies on words—spoken or written labels for the concepts we intend to convey. These linguistic units map meanings onto forms that can be recognized and produced by others within a shared communication system. To make this possible, words are stored in long-term memory within what is often called the mental lexicon. This repository includes orthographic, phonological, morphological, and semantic information, and enables retrieval whenever comprehension or production demands it. The act of retrieving such information is what researchers describe as lexical access. In reading, the orthographic stimulus must be matched with its stored representation, just as the phonological form of the acoustic signal must be matched during speech comprehension. In production, by contrast, the intended meaning serves as the entry point, giving access to the phonological or orthographic form required for speech or writing. The term lexical access was first popularized in studies of visual word recognition, but its use has since expanded. In current literature, especially on word recognition, alternative terms such as lexical retrieval or lexical processing are often preferred, since access implies a discrete lexical entry that can be “looked up.” This assumption is at odds with many contemporary models, which favor distributed, parallel-activation accounts where sublexical units such as letters, phonemes, or morphemes contribute dynamically to recognition. In contrast, in word production the notion of access is less contentious, because selecting the correct lexical item from meaning necessarily requires pinpointing a specific representation. Research into lexical processing has focused on two main questions: the nature of the stored representations in the mental lexicon and the cognitive procedures through which they are retrieved. Much of this work has been conducted by cognitive psychologists, leading to an emphasis on mechanisms of retrieval rather than linguistic content. Moreover, explanations have focused on the cognitive rather than the neural level, though psycholinguistic theories are increasingly informed by neuroscience. Indeed, although the present article emphasizes cognitive perspectives—as suggested by its title—key findings on neural and electrophysiological correlates of lexical processing are also acknowledged, since they have substantially contributed to refining and constraining cognitive theories. The bulk of empirical research has concentrated on visual word recognition, not only because reading experiments offer precise control and measurement, but also because of their pedagogical and societal importance. Nevertheless, the same theoretical questions extend to spoken word recognition, speech production, and writing, each of which poses its own challenges for models of lexical access. In recent years, important advances have reshaped the field: large-scale megastudies and open-access lexical databases now allow researchers to examine the joint influence of multiple lexical and semantic variables, moving beyond traditional factorial designs. Computational modeling has also become more diverse, integrating Bayesian frameworks, hybrid connectionist approaches, and deep learning architectures, while empirical work has expanded to a wider range of languages and writing systems. The references selected throughout this article represent either foundational studies that shaped the field or recent contributions that capture the current state of debate, providing a framework for understanding how humans connect word forms to meanings in real time. Updated in September 2025 by Maria Fernández-López.