WordNet sense 1 (the value below which 50% of the cases fall):

WordNet sense 2 (relating to or constituting the middle value of an ordered set of values (or the average of the middle two in a set with an even number of values)):

WordNet sense 3 (conforming with or constituting a norm or standard or level or type or social norm; not abnormal):

WordNet sense 4 (dividing an animal into right and left halves):

WordNet sense 5 (in or near a center or constituting a center; the inner area):