step vs pace

step and pace both are nouns.

Word	Noun	Adjective	Verb	Adverb
step	Yes	No	Yes	No
pace	Yes	No	Yes	No

As nouns, pace is a hyponym of step; that is, pace is a word with a more specific, narrower meaning than step:

Other hyponyms of step include stride, tread, pas, trip, sidestep, footstep.

As nouns, step and pace are synonyms defined as:

Other synonyms of step include footstep, stride.

As verbs, step and pace are synonyms defined as:

step (noun)	pace (noun)
the act of changing location by raising the foot and setting it down	a step in walking or running
any maneuver made as part of progress toward a goal	the relative speed of progress or change
a sequence of foot movements that make up a particular dance	a unit of length equal to 3 feet; defined as 91.44 centimeters; originally taken to be the average length of a stride
support consisting of a place to rest the foot while ascending or descending a stairway	the distance covered by a step
a solid block joined to the beams in which the heel of a ship's mast or capstan is fixed	the rate of moving (especially walking or running)
a musical interval of two semitones	the rate of some repeating event
a mark of a foot or shoe on a surface
the sound of a step of someone walking
the distance covered by a step
a short distance
relative position in a graded series

step (verb)	pace (verb)
measure (distances) by pacing	measure (distances) by pacing
move or proceed as if by steps into a new situation	regulate or set the pace of
place (a ship's mast) in its step	walk with slow or fast paces
shift or move by taking a step	go at a pace
put down or press the foot, place the foot
walk a short distance to a specified place or in a specified manner
move with one's feet in a specific manner
furnish with steps
treat badly
cause (a computer) to execute a single command