Terminology
New or Recently Introduced Terms 
 Area (the amount of two-dimensional space in a bounded region)

 Area model (a model for multiplication that relates rectangular arrays to area) 
 Square unit (a unit of area—specifically square centimeters, inches, feet, and meters)

 Tile (to cover a region without gaps or overlaps) 

     Unit square (e.g., given a length unit, it is a 1 unit by 1 unit square)

 Whole number (an integer, i.e., a number without fractions)