Definition
Meaning is the relationship between a linguistic expression and what it conveys — but logic and the philosophy of language quickly discovered that this single word collects several distinct relationships that must be kept apart. Frege famously separated sense (the mode of presentation, the way an expression picks out its referent) from reference (the object or value the expression actually picks out). Two expressions can share a referent but differ in sense — "the morning star" and "the evening star" both refer to Venus, but they carry different information.
Later twentieth-century philosophy added further refinements: truth-conditional meaning treats the meaning of a sentence as the conditions under which it would be true; use-theoretic meaning, associated with the later Wittgenstein, locates meaning in the practices and contexts in which words are deployed.
Why it matters
How it works
The truth-conditional approach, dominant in modern formal semantics, holds that to know the meaning of a declarative sentence is to know the conditions under which it would be true. This converts the question "what does this sentence mean?" into the question "what would the world have to be like for it to count as true?" The advantage of this move is precision: truth conditions can be specified formally and compared across sentences, supporting the systematic analysis of inference. Davidson built an entire programme of semantic theory on this foundation.
The use-theoretic approach pushes back. Wittgenstein argued that the meaning of a word is its use in the language game — its function within a practice rather than its abstract relation to objects. The two approaches are not exclusive. Truth conditions explain what makes assertions true; uses explain why we make them, how we coordinate, and how meaning shifts as practices evolve. For logic, the truth-conditional analysis is indispensable because validity is defined truth-functionally. For the broader philosophy of language, both perspectives are needed to capture the full phenomenon of human communication.