In a parallelogram, the diagonals bisect each other. This means that the point where the diagonals meet (point A in this case) divides each diagonal into two equal parts.
Since WY measures 7 centimeters, the length of AW (which is half of the diagonal WY) can be calculated as follows:
\[ AW = \frac{WY}{2} = \frac{7 \text{ cm}}{2} = 3.5 \text{ cm} \]
Thus, the length of AW is 3.5 cm.