Fat-soluble vitamin and Vitamin D

Fat-soluble vitamin noun - Any vitamin that is soluble in fats.

Vitamin D and fat-soluble vitamin are semantically related. In some cases you can replace phrase "Vitamin D" with "Fat-soluble vitamin", this phrases are similar.

Vitamin D noun - A fat-soluble vitamin that prevents rickets.

Fat-soluble vitamin and vitamin D are semantically related. You can use "Fat-soluble vitamin" instead a noun phrase "Vitamin D".