The option b) 'one-to-one relationship between symbol and meaning' is not a key property of language. Language includes properties like arbitrary symbol-concept relationships, multilevel structures, and high productivity that enable expressive and flexible communication.
The key property of language that is not defined in the lecture is: b) one-to-one relationship between symbol and meaning. Language properties typically include an arbitrary relationship between symbol and concept referred to, structure at multiple levels, and virtually limitless productivity.
These properties allow for complex and flexible communication, where symbols can have multiple meanings depending on context, and new sentences can be created endlessly.
Unlike mathematical symbols, which are interchangeable labels with no intrinsic meaning, linguistic symbols are part of a system that has rules, such as grammar, that must be followed to convey meaning effectively.