Cut the Knot
Cut the Knot!: Mathematics as a Language
A sophisticated discussion on the language of mathematics, its origins, meanings, and precision.
Other
Austin Community College: Mathematical Language
Austin Community College provides a few paragraphs on mathematical language, the importance of learning it, and the importance of using it correctly.
University of Cambridge
University of Cambridge: Nrich: Writing Digits
At this one page website you must know the difference between digits and numbers to solve the challenge. When you have a solution you can check it with the solution right there on the website.