Language & Definitions (Dictionaries)

It is essentail that teacher introducce children to matematical language and the following may help:

This comprehensive Maths Dictionary, linking games and puzzles with definitions has been put together by maths specialists from the University of Oxford in the UK:
https://www.mathsisfun.com/definitions/letter-c.html 

This Maths Dictionary produced with permission by Jenny Eather Maths teacher in Australia provides definitions and examples: 
http://www.amathsdictionaryforkids.com

NRich initiated by staff at the UK University Cambridge has an extensive range of activities for all ages. Nrich site is a rich, research informed site with guidance for maths teachers and a wealth of resources for use in classroom practice, (https://nrich.maths.org).

NCETM (https://www.ncetm.org.uk/ ) is a similar site focused on the development of mathematics teachers through the dissemination of research and guidance.