What word describes the equal shares of the shape

We can position the circles and rectangles into equal shares of two, three and four and so on. Halves, thirds, half of, a third of, etc words are used to describe the equal shares. A fraction also describes the division of wholes into equal shares as the image shows the rectangle is divided into 4 equal parts and one part is defined as one fourth of the shape.

She should use 12/3 to measure