To determine the measure of an interior angle in a regular decagon, you can divide the total sum of the interior angles by the number of sides, which in this case is $10$.

A regular decagon is a ten-sided polygon where all sides and angles are equal. To calculate the measure of each interior angle, you first need to find the total sum of all interior angles. The formula for the sum of interior angles in any polygon is given by:

$(n-2) \times 180^\circ$

where $n$ represents the number of sides. For a decagon, with $n = 10$, the calculation is as follows:

$(10-2) \times 180^\circ = 8 \times 180^\circ = 1440^\circ.$

Now, since a regular decagon has equal angles, you can find the measure of each interior angle by dividing the total sum of the interior angles by the number of angles (or sides), which is $10$:

$\frac{1440^\circ}{10} = 144^\circ.$

Thus, each interior angle in a regular decagon measures $144$ degrees. This approach not only illustrates how to apply the formula for the sum of interior angles but also emphasizes the process of finding the measure of each angle in a regular polygon.