Exoskeleton of cicada attached to Tridax procumbens. An exoskeleton (from Greek Î­Î¾Ï, Ã©xÅ outer and ÏÎºÎµÎ»ÎµÏÏÏ, skeletos skeleton) is the external skeleton that supports and protects an animal's body, in contrast to the internal skeleton (endoskeleton) of, for example, a human. In usage, some of the larger kinds of exoskeletons are known as shells.
The term arbitrary here refers to the fact that the symbol that people use is made or chosen without any principle, logic or reason. For example, people in Java do not have a principle or logic to call an animal with long tail, two hands, and two legs and like scratching and playing on trees as kethek.o, to answer Daniel's question: English people do not have any reason why they call the animal that produces meauwww as cat. Again, this is because language is arbitrary: no logical reason is used when choosing a symbol, and no direct relationship between the symbol and the symbolized.
Infinity symbol â. Infinity â is a maths text symbol for an infinite number that people had been texting from the times when ASCII encoding was developed. And you can type it right from your keyboard. I'll show you how to do it by using different techniques depending on your Operating System and tastes.