step vs tread

step and tread both are nouns.

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

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

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

As verbs, step and tread are synonyms defined as:

step (noun)	tread (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	structural member consisting of the horizontal part of a stair or step
a sequence of foot movements that make up a particular dance	the part (as of a wheel or shoe) that makes contact with the ground
support consisting of a place to rest the foot while ascending or descending a stairway	the grooved surface of a pneumatic tire
a solid block joined to the beams in which the heel of a ship's mast or capstan is fixed
a musical interval of two semitones
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)	tread (verb)
measure (distances) by pacing	crush as if by treading on
move or proceed as if by steps into a new situation	brace (an archer's bow) by pressing the foot against the center
place (a ship's mast) in its step	mate with (used of male birds)
shift or move by taking a step	tread or stomp heavily or roughly
put down or press the foot, place the foot	put down or press the foot, place the foot
walk a short distance to a specified place or in a specified manner	apply (the tread) to a tire
move with one's feet in a specific manner
furnish with steps
treat badly
cause (a computer) to execute a single command