front 1 area  back 1 The amount of square units needed to cover a figure. The area of this shape is 6 square units. 
front 2 centimeter  back 2 A small unit of metric measurement. Benchmark: across your pinky nail

front 3 cup  back 3 A cup is a small customary unit of liquid capacity. The milk cartons you buy in the cafeteria hold 1 cup of milk. The abbreviation for cup is c. 
front 4 degrees  back 4 units used to measure temperature

front 5 estimate  back 5 A close guess of the actual value, usually with some thought or calculation involved. 
front 6 foot  back 6 A customary unit of measure for length.

front 7 gallon  back 7 A customary unit of measure for liquid capacity.

front 8 gram  back 8 A metric unit of mass. One sheet of paper = 1 gram.

front 9 inch  back 9 A customary unit of measure for length. 1 inch = from your knuckle to the end of your thumb.

front 10 kilogram  back 10 A metric unit of mass. 1 kilogram = the weight of 1 math book

front 11 kilometer  back 11 A large metric unit of length. 1 kilometer = 1000 meters

front 12 length  back 12 the distance between 2 points, how long something is,

front 13 liter  back 13 A metric unit of capacity. Pop comes in 2 liter bottles.

front 14 meter  back 14 A metric unit of length. 100 centimeters = 1 meter

front 15 mile  back 15 A large customary unit of length. Miles are used to measure the distance between cities. The abbreviation for mile is m. 
front 16 ounce  back 16 An ounce is a small customary unit of weight. A key weighs about 1 ounce.

front 17 perimeter  back 17 The distance around the outside of a shape. Perimeter is measured in units. Add the lengths of all the sides to get the perimeter. 
front 18 pounds  back 18 A customary unit for weight. 1 pound is able the weight of a loaf of bread.

front 19 quart  back 19 A customary measure for capacity. 1 quart = 2 pints

front 20 volume
 back 20 The volume of a container measured in liquid units

front 21 weight
 back 21 How heavy an object is

front 22 yard  back 22 A customary unit of length. 1 yard = 3 feet or 36 inches

front 23 a.m.  back 23 Is the half of the day from midnight to midday. What we call night and morning.

front 24 p.m.  back 24 Is the half of the day from Midday to Midnight.

front 25 elapsed time  back 25 The amount of time between the beginning and the end of an event 
front 26 pint  back 26 A customary measure of liquid capacity. You would need to buy 2 cartons of milk in the cafeteria to get a pint of milk.

front 27 temperature  back 27 
front 28 balance scale  back 28 set of scales used to measure weight 
front 29 Celcius  back 29 metric unit for measuring temperature 
front 30 Fahrenheit  back 30 customary unit for measuring temperature 
front 31 quarter hour  back 31 15 minutes before or after the hour 