( ( ( ( ( ( Our ( natural concept ) ) ( of time ) ) ( is ( linked ( to ( ( the rotation ) ( of ( the earth ) ) ) ) ) ) ) and ) ( we ( define ( ( ( the length ) ( of ( ( the day ) ( as ( the ( 24 hours ) ) ) ) ) ) ( it ( takes ( the ( earth ( to ( ( spin once ) ( on ( its axis ) ) ) ) ) ) ) ) ) ) ) ) . )
(ROOT (S (S (NP (NP (PRP$ Our) (JJ natural) (NN concept)) (PP (IN of) (NP (NN time)))) (VP (VBZ is) (VP (VBN linked) (PP (TO to) (NP (NP (DT the) (NN rotation)) (PP (IN of) (NP (DT the) (NN earth)))))))) (CC and) (S (NP (PRP we)) (VP (VB define) (NP (NP (DT the) (NN length)) (PP (IN of) (NP (NP (DT the) (NN day)) (PP (IN as) (NP (DT the) (CD 24) (NNS hours))))) (SBAR (S (NP (PRP it)) (VP (VBZ takes) (NP (DT the) (NN earth) (S (VP (TO to) (VP (VB spin) (ADVP (RB once)) (PP (IN on) (NP (PRP$ its) (NNS axis))))))))))))) (. .)))
Our natural concept of time is linked to the rotation of the earth and we define the length of the day as the 24 hours it takes the earth to spin once on its axis.
(ROOT (S (NP (NNP Earth)) (VP (VBZ rotates) (PP (PP (IN on) (NP (PRP$ its) (NNS axis)) (ADVP (RB once))) (CC times) (PP (IN in) (NP (CD one) (NN day))))) (. .)))