( ( ( A pair ) ( of scissors ) ) ( ( is ( a ( compound machine ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (NN pair)) (PP (IN of) (NP (NNS scissors)))) (VP (VBZ is) (NP (DT a) (JJ compound) (NN machine))) (. .)))
A pair of scissors is a compound machine.
(ROOT (S (NP (NNS Scissors)) (VP (VBP are) (NP (JJ compound) (NNS machines))) (. .)))