It is important to learn how different verbs are used in writing.
The most familiar use of the verbs wax and wane is in reference to the states of the moon.
To wax is to grow. To wane is to diminish.
The moon has four phases, also called quarters. During the first two quarters, the moon is said “to wax” as its light increases. During the third and fourth quarters, as its light decreases, the moon is said “to wane.” Read more.