middle

Equally distant from extremes or limits; central.

Being at neither one extreme nor the other, as of a sequence or scale; intermediate.

Of or relating to a division of geologic time between an earlier and a later division.

Of or relating to a stage in the development of a language or literature between earlier and later stages.

Of, relating to, or being a verb form or voice in which the subject both performs and is affected by the action specified.