Time (noun) Old English tima "space of time," from Proto-Germanic timon-"time" from root  da  "to divide"

1): the indefinite continued progress of existence and events in the past, present, and future regarded as a whole.

2): a point of time as measured in hours and minutes past midnight or noon.

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Time has been debated by philosophers  long before modern physics. But a century ago Einstein is purported to have said, "Time is the fourth dimension." 

     There is no question as to the accuracy of this statement but, due to the prevalence of "non-scientific" science fiction, the general public has become confused as to what a "dimension" is.  Most think of a dimension as a place, much like the world Alice found when she entered the looking-glass.  This is totally wrong. Examples: width, depth and height are dimensions.

     A dimension is not a place, it is a measurement . When we speak of dimensions we are referring to the various measurements that may be made, such as length, motion, mass, etc.

      One can no more travel in tme than one can travel in cubic measurements.

     Time is the measurement of motion. When we speak of how much tima an action took, we are comparing its motions to the motions of other things. For instance, a clock does not measure "time",at all. The movement of its hands correspond symbolically to the rotation of the Earth on its axis.

     A clock does not measure "time". Its movement represents  The prevailing view in physics has been that time )T) serves as the fourth dimension of space, represented mathematically as 4D.  Einstein said,"Time is the fourth dimension."  When he said that he was not interpretting time (T) as a fourth dimension of space. Space is not 3D + T, instead, it is 4D. With clocks we measure numerical order of material change. This numerical order is the only time that exists in a physical world. With this approach all immediate information transfers of quantum physics are explained in a more appropriate way. 4D space is a medium of quantum information transfers. Simply stated, the first three dimensions are used to specify an object’s location/movement in space (forward-backwards, left-right and up-down), while the fourth dimension locates its position in time. All four dimensions are used to specify completely the location or dynamism of an object in space. Collectively the four dimensions are inseparably interlinked and known as space-time.

      We are living in a three dimensional world, (possessing length, width and height), so we are unable to see the fourth dimension, as our physical world is constructed within these three physical dimensions only. We might feel or imagine time’s presence, but we can never actually detect it with our three-dimensional senses because it extends beyond our universe. We can only perceive time - the fourth dimension - as memories lodged at different intervals, with the result we perceive time moving in one direction - forward. A demonstration of four dimensional space-time’s inseparability is the fact that we cannot look into space without looking back in time - like we see the Moon as it was ~1.2 seconds ago and the Sun as it was ~8 minutes ago and so on.