Q. What does the (n.d.) mean?
In an APA reference or citation, n.d. stands for "no date."
You use n.d. when you cannot find a publication date on the source you are trying to reference and cite; it stands in for the year that is normally in the date position.
Here is an example reference entry with no publication date available:
Willemssen, J. (n.d.). The joy of chicken eggs in prehistoric times. http://url