Math Dictionary for Kids

http://www.amathsdictionaryforkids.com/dictionary.html

 

Math is Fun

http://www.mathsisfun.com/

 

Khan Academy

http://www.khanacademy.org/

 

Big Ideas Student Online

https://www.bigideasmath.com/students/

 

IXL Math Practice

https://www.ixl.com/math/