Allison is quite correct, but I'd like to give you some examples: Medium temperature (on a stove, oven or heater) is in the middle. Note that your oven doesn't have an average temperature setting ! Someone asks how you feel, and you can say "pretty average". It means that you are not feeling very good or very bad, but you cant say you feel "pretty medium". Andrew.

Medium = related to the middle average = usual, ordinary

Examples... I wear a sized medium shirt.... He is not ugly, nor is he very beautiful, he is just average looking.

Hello! "Medium" is the middle size or amount of something. Small, medium, large. "Average" is what is most common after adding everything up. So if you have 5 large shirts, 3 medium shirts and 20 small shirts, the average size of those shirts is small. Or thereabouts. Or another example: if you have 5 people who are 1.9m tall and 5 people who are 1.5m tall, there is no "medium" height between those 10 people, but the "average" height is 1.7m. No 1.7m tall person exists in that group, but that's mathematics for you. ;)