I see in some journals that mention the line spacing in MS Word in terms of "nk". What does that mean and how can I set that in the Word?

It's been just over five years since I joined the Stack Exchange network. I was awarded my fifth Yearling badge, over at Science Fiction & Fantasy, around a week ago. I became interested in the upkeep and moderation of the site not long after. One thing led to another, and I was appointed to mode...