What is the difference between stock and broth?

If you google this question you get a whole raft of answers (of course) which do not really give a defined answer. Some say that stock is made from bones and broth is made from meat, others say broth contains vegetables but stock doesn't. 

The liquid served with pho is universally known as a broth rather than a stock, although once you construct your whole bowl I would say the end result is a noodle soup.

I think the key differences between Phomo's pho broth and a stock are:

• We do not roast our bones before cooking. To get a deeper stockier flavour which is ideal as a sauce / gravy base (think Bisto) you should roast your bones first. For pho, we are aiming for a smoother lighter flavour that enables the spices to come through. Cooking the bones raw maintains all of the bones goodness into the pho.
• We very gently simmer the broths for up to 8 hours. For stock I tend to boil vigorously until it has reduced which usually takes an hour or 2. Both result in a lovely gelatinous liquid once cooled.
• Bone:water ratio - for stock I would use 2 litres of water per kg of bones. For our pho broth we use around 1.4 litres per kg of bones, meaning there is lots more meat in our pho broth.
• Colour - the colour of stock is a deep dark brown which comes from both the pre-roasting of the bones and the vigorous boiling. Our pho broth tends to be more caramel coloured, although don't hold us to that - small batch cooking means a slightly different outcome every time, but we taste test constantly to ensure that, whatever the colour, our broth is the pho'king best!

And as someone else wisely said today, a good way of looking at it, is that a stock forms a base of something - a gravy or a sauce, but broth is ready as it is.

What do you think is the difference between stock and broth?