Why is second abbreviated 2d instead of second?

You're likely thinking of the abbreviation 2D which stands for two-dimensional. This is a common abbreviation in various fields like computer graphics, art, and geometry.

"Second" is usually abbreviated as sec or s.

The abbreviation "2D" is used to describe objects or spaces that have length and width but no depth. For example, a picture on a screen is 2D because it only has length and width, not depth.

Let me know if you have any other questions!