fourth dimension(redirected from 4-D geometry)
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1. the dimension of time, which is necessary in addition to three spatial dimensions to specify fully the position and behaviour of a point or particle
2. the concept in science fiction of a dimension in addition to three spatial dimensions, used to explain supranatural phenomena, events, etc.
fourth dimension[¦fȯrth də′men·chən]
Time in the theory of relativity, in which space and time are conceived as particular aspects of a four-dimensional world.