Many animal and even plant species communicate with each other. Humans are not unique in this capability. However, human language is unique in being a symbolic communication system that is learned instead of biologically inherited. Symbols click this icon to hear the preceding term pronounced are sounds or things which have meaning given to them by the users. Originally, the meaning is arbitrarily assigned. For instance, the English word "dog" does not in any way physically resemble the animal it stands for. All symbols have a material form but the meaning can not be discovered by mere sensory examination of their forms. They are abstractions.