The phrase "number concept" refers to the understanding of what numbers represent and how they relate to each other. It involves knowing the order of numbers, their value, and how they can be combined or separated to perform operations like addition, subtraction, multiplication, and division.
On the other hand, "number sense" refers to the ability to use numbers flexibly and effectively in various contexts. It goes beyond just knowing the numerical facts and focuses on understanding the relationships between numbers and their magnitude. Number sense involves estimating, comparing, and making sense of numbers in real-world situations.