( ( ( Quadruplet ( , Quad ) ) ( ( A tandem ) ( for ( four riders ) ) ) ) . )
(ROOT (NP (NP (NNP Quadruplet) (, ,) (NNP Quad)) (NP (NP (DT A) (NN tandem)) (PP (IN for) (NP (CD four) (NNS riders)))) (. .)))
Quadruplet, Quad A tandem for four riders.
(ROOT (S (NP (NP (CD Four) (NNS children)) (VP (VBN born) (PP (IN at) (NP (CD one) (NN birth))))) (VP (VBP are) (VP (VBN called) (NP (NNS quadruplets)))) (. .)))