Acute angle:
An acute angle is an angle that measures less than 90 degrees. It is smaller than a right angle but bigger than a straight angle.

Example of an acute angle:
Let's consider an angle that measures 60 degrees. This angle is less than 90 degrees, so it falls into the category of an acute angle.

Explanation:
To understand the concept of an acute angle, it is important to have a basic understanding of angles. An angle is formed when two lines or line segments meet at a point. The point where the lines meet is called the vertex of the angle. The two lines or line segments that form the angle are called the arms of the angle.

An angle can be classified based on its measure. In this case, we are focusing on acute angles. Acute angles are angles that are less than 90 degrees. They are sharp angles that are smaller than a right angle.

To give an example, let's consider an angle that measures 60 degrees. This means that if we were to measure the angle with a protractor, it would be opened to 60 degrees. Since 60 degrees is less than 90 degrees, it falls into the category of an acute angle.

In geometric terms, acute angles are often found in triangles and other polygons. They are important in determining the properties and relationships of shapes. Acute angles can also be found in real-life situations, such as the angle formed by the hands of a clock at a certain time or the angle of a roof slope.

In summary, an acute angle is an angle that measures less than 90 degrees. It is smaller than a right angle and bigger than a straight angle. An example of an acute angle is an angle that measures 60 degrees.