Spoken and written language are incredible tools for humanity. They let us efficiently communicate concepts to each other, coordinate activities, and generally work together more effectively. But an important part of keeping language effective is having standards that everyone recognizes. Dictionaries give us a vocabulary to work from and they standardize the meanings and spellings of words. Grammar books set up the rules of our language to help us avoid unintentional ambiguity and keep misunderstandings from happening.Visual Language Standards
In the same way, dictionaries and grammar rules have been set up for verbal language, visual language also has standards. Arguably, the two most important of these for charts commonly seen in graphic design are the Semiology of Graphics, and the ISOTYPE standard.