( They ( ( are ( learning ( ( ( that ( machines ( make ( work easier ) ) ) ) and ) ( that ( ( many machines ) ( are ( ( a series ) ( of ( simple machines ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBP are) (VP (VBG learning) (SBAR (SBAR (IN that) (S (NP (NNS machines)) (VP (VBP make) (S (NP (NN work)) (ADJP (RBR easier)))))) (CC and) (SBAR (IN that) (S (NP (JJ many) (NNS machines)) (VP (VBP are) (NP (NP (DT a) (NN series)) (PP (IN of) (NP (JJ simple) (NNS machines)))))))))) (. .)))
They are learning that machines make work easier and that many machines are a series of simple machines.
(ROOT (S (S (NP (DT A) (JJ complex) (NN machine)) (VP (VBZ is) (VP (VBN described) (PP (IN by))))) (: :) (S (NP (PRP it)) (VP (VBZ is) (VP (VBN made) (PP (IN of) (NP (QP (JJR more) (IN than) (CD one)) (JJ simple) (NN machine)))))) (. .)))
A complex machine is described by: it is made of more than one simple machine.