Define medium (plural: media)

the intervening substance through which impressions are conveyed to the senses or a force acts on objects at a distance.

Explanation:

Arrange your numbers in numerical order.

Count how many numbers you have.

If you have an odd number, divide by 2 and round up to get the position of the median number.

If you have an even number, divide by 2. Go to the number in that position and average it with the number in the next higher position to get the median.

i think it's about 10 mins.

actually i think that's wrong, but i don't know how to delete this.

but who knows it might be right.