Human language has several unique properties that distinguish it from animal communication systems. Human language allows for displacement by referring to things and events not present, it is arbitrary where linguistic forms are not inherently related to their meanings, and it is productive allowing for infinite novel utterances. In contrast, animal communication involves limited, fixed signals tailored to the current time and place. Additionally, human language is acquired culturally rather than instinctively and has a duality of distinct sounds and meanings organized at two levels.