( ( Quantum mechanics ) ( ( is ( ( a set ) ( of ( principles ( ( describing ( physical reality ) ) ( at ( ( the ( atomic level ) ) ( of ( ( ( ( matter ( -LRB- ( ( ( molecules and ) atoms ) -RRB- ) ) ) and ) ( the subatomic ) ) ( -LRB- ( ( ( ( ( ( electrons , ) protons ) , ) and ) ( even ( smaller particles ) ) ) -RRB- ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Quantum) (NNS mechanics)) (VP (VBZ is) (NP (NP (DT a) (NN set)) (PP (IN of) (NP (NP (NNS principles)) (VP (VBG describing) (NP (JJ physical) (NN reality)) (PP (IN at) (NP (NP (DT the) (JJ atomic) (NN level)) (PP (IN of) (NP (NP (NN matter)) (PRN (-LRB- -LRB-) (NP (NP (NNS molecules)) (CC and) (NP (NNS atoms))) (-RRB- -RRB-)) (CC and) (NP (DT the) (NN subatomic)) (PRN (-LRB- -LRB-) (NP (NP (NNS electrons)) (, ,) (NP (NNS protons)) (, ,) (CC and) (NP (RB even) (JJR smaller) (NNS particles))) (-RRB- -RRB-))))))))))) (. .)))
Quantum mechanics is a set of principles describing physical reality at the atomic level of matter (molecules and atoms) and the subatomic (electrons, protons, and even smaller particles).
(ROOT (S (NP (NP (DT The) (JJ specialized) (NN study)) (PP (IN of) (NP (NP (DT the) (NN motion)) (PP (IN of) (NP (NP (NNS objects)) (SBAR (WHNP (WDT that)) (S (VP (VBP are) (ADJP (JJ atomic/subatomic) (PP (IN in) (NP (NN size)))))))))))) (VP (VBZ is) (VP (VBN called) (NP (NN quantum) (NNS mechanics)))) (. .)))
The specialized study of the motion of objects that are atomic/subatomic in size is called quantum mechanics.