shortness; brevity
The quality or degree of being short in length, duration, or conciseness. Used for physical length, time, or abstract brevity.
The shortness of this skirt is just right.
I was surprised by the brevity of the meeting.
短さ describes shortness, the direct opposite of 長さ (length).
Derived from the adjective 短い (みじかい, 'short') by adding the nominalizing suffix さ, which forms a noun expressing the degree or quality of the adjective.