1. Arbitrariness: The connection between a word and its meaning is arbitrary. There's no inherent reason why "cat" refers to a feline creature, or why "arbre" means "tree" in French. This arbitrary relationship allows for flexibility and change in language over time.
2. Productivity: Humans can create and understand an infinite number of novel sentences and expressions. We can combine words in new ways to communicate complex ideas, even about things we've never encountered before.
3. Displacement: We can talk about things that are not present in the here and now, including past events, future possibilities, and abstract concepts. This allows us to share information, tell stories, and plan for the future.
4. Duality of Structure: Languages have two levels of organization: sounds (or signs) and meaning. Sounds are combined into meaningful units (words), and words are combined into larger units (sentences), expressing complex thoughts and ideas.
It's important to note that these characteristics are not absolute. Some languages might have unique features that make them seem less arbitrary or less productive in certain ways. However, these four characteristics are widely considered to be fundamental to human language, and they play a key role in our ability to communicate effectively.