Variable - When a letter is used to represent a number or number in equations and or expressions. E.g., in 3x + y, both y and x are the variables.
Venn Diagram - A Venn diagram is often two circles (can be other shapes) that overlap. The overlapping part usually contains information that is pertinent to the labels on both sides of the Venn diagram. For instance: one circle could be labeled 'Odd Numbers', the other circle could be labeled 'Two Digit Numbers' the overlapping portion must contain numbers that are odd and have two digits. Thus, the overlapping portions shows the relationship between the sets. (Can be more than 2 circles.)
Volume - A unit of measure. The amount of cubic units that occupy a space. A measurement of capacity or volume.
Vertex- A point of intersection where two (or more) rays meet, often called the corner. Wherever sides or edges meet on polygons or shapes. The point of a cone, the corners of cubes or squares.