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Acute angle- An angle that is measured less than 90 degrees.

Add- To make a number larger by a certain amount. For example 2+2=4.

Addend- One of two or more numbers that are added. For example in 5+3+1, one addend.

Adjacent angles- Angles that are next to each other; adjacent angles have a common side, but no other overlap.

Algebraic expression- An expression that contains a variable. For example, if Maria is 2 inches taller than Bob, and the variable m represents Maria’s height, then the algebraic expression m-2 represents Bob’s height.

Angle- A figure that is formed by two rays or two line segments with a common endpoint. The common endpoint is called the vertex of the angle. An acute angle has a measure greater than 0 degrees and less than 90 degrees. An obtuse angle has a measure greater than 90 degrees and less than 180 degrees. A reflex angle has a measure greater than 180 degrees and less 360 degrees. A right angle measures 90 degrees. A straight angle measures 180 degrees.