Question

what is a symbol used in writing?

Answer 1

Are you asking about symbols used in ancient writing?

If you are, an example is hieroglyphics (don't trust me that I spelled that right).

Hope I helped you!

Answer 2

thanks!!

Answer 3

There was also cuneiform writing.
http://images.google.com/images?q=cuneiform&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&sa=X&oi=image_result_group&resnum=4&ct=title

And today there are various alphabets and symbol systems. Ours (in modern day English) is referred to as the Roman alphabet although ours has a couple of letters the Romans didn't have.
http://www.google.com/search?q=roman+alphabet&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

http://www.google.com/search?q=greek+alphabet&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

http://www.google.com/search?q=russian+alphabet&ie=utf-8&oe=utf-8&aq=t&rls=org.mozilla:en-US:official&client=firefox-a

and there are many others.

Our modern English alphabet has 26 pairs of symbols for letters (sounds) and ten symbols for numbers.