Middle; medium; half.
[Old English midd, of Germanic origin.]
Examples include midwinter; midfield; midweek; midstream; midway; midlife, the central period of a person's life, say between 45 and 60 years old; midriff (Old English hrif, belly), the region between the chest and the waist; and mid-Atlantic, in the middle of the Atlantic ocean. In mid-air the sense is less precise. In midwife the first element comes from the obsolete Middle English preposition mid, with.