mid·point 
(mĭdpoint′)
(mĭdpoint′)n.
1. Mathematics The point of a line segment or curvilinear arc that divides it into two parts of the same length.
2. A position midway between two extremes.
- heteroatom
- heterocercal
- heterochromatic
- heterochromatin
- heterochromatism
- heterochromosome
- heterochronic
- heterochronous
- heterochrony
- heterocycle
- heterocyclic
- heterocyst
- heterodactyl
- heterodactylous
- heterodactyly
- heterodox
- heterodoxy
- heterodyne
- heteroecious
- heteroecism
- heterogamete
- heterogametic
- heterogamic
- heterogamous
- heterogamy