Mathwords
This website is designed for math students who need an easy-to-use, easy-to-understand math resource all in one place. It is a comprehensive listing of formulas and definitions from beginning algebra to calculus. The explanations are readable for average math students, and over a thousand illustrations and examples are provided.
Existing math reference resources are no help for most math students.
Professional math reference guides are excellent for advanced students and professionals. They are useless, however, for the vast majority of math students. Authors of professional guides are unforgiving in their use of technical language, so the definitions are difficult to read.
Textbooks aren’t much help, either. They usually have appendices of formulas and/or glossaries, but these are an afterthought and seldom are helpful. Often the topic a student wants to look up is not covered because it is too elementary. Back-of-the-book glossaries are usually terse, technical, and have no illustrations or examples. They are only helpful to students who already know the material. The arrangement and content of textbook appendices tends to discourage average math students from using them.
For more details click here