I have found these words being mixed up in all sorts of contexts, from instructions to posters, and in all sorts of texts. I’ve also needed to look up which is which when following exercise or yoga instructions! Do you know the difference between prone and supine and do you use them appropriately? Or are they in fact different in the end at all?
Here’s another in my series of Troublesome Pairs to help you (and remember: if you have one for me, check the index then do send it over!).
Prone and supine both mean lying flat. But which way up, that’s the question.
Prone means lying flat, especially face downwards (Oxford Dictionaries). Collins online goes straight to the face-down aspect. Merriam-Webster have it as lying prostrate (adjective) or flat, and a second definition of lying front-downwards. According to all three of them, prostrate means lying flat with the face downwards (you prostrate yourself in front of an emperor, an altar, etc., so that makes sense, and Merriam-Webster, which is bigger than my one-volume Oxford, adds the air of worship to its definition, while Collins adds it to a definition of “prostrating yourself”).
Supine is unequivocably defined as lying flat, face upwards.
So prone can mean lying flat OR lying flat, face downards, prostrate adds an air of worship or respect and supine only means lying flat, face upwards.
You can find more troublesome pairs here and the index to them all so far is here.