This chapter presents a summary of current theories and future directions for research into how humans represent and process word meaning (lexico-semantics). The chapter begins with a review of theoretical approaches from cognitive and developmental psychology, cognitive neuroscience, and computational sciences. Three core issues are identified that theories need to account for: (1) how to characterize non-verbal concepts and lexico-semantics; (2) the cognitive and neural format of lexico-semantic representations; and (3) whether lexico-semantics is fundamentally independent of context (Is there is a fixed “core” of what a word means?) or fundamentally dependent on context (Does word meaning change depending on how it is used?). We conclude that a useful direction for future research will be to carefully consider how words change with their context of use.