( ( A year ) ( ( ( is ( ( the length ) ( of time ) ) ) ( that ( it ( takes ( Earth ( to ( ( make ( a ( complete revolution ) ) ) ( around ( the Sun ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT A) (NN year)) (VP (VBZ is) (NP (NP (DT the) (NN length)) (PP (IN of) (NP (NN time)))) (SBAR (IN that) (S (NP (PRP it)) (VP (VBZ takes) (S (NP (NNP Earth)) (VP (TO to) (VP (VB make) (NP (DT a) (JJ complete) (NN revolution)) (PP (IN around) (NP (DT the) (NNP Sun)))))))))) (. .)))
A year is the length of time that it takes Earth to make a complete revolution around the Sun.
(ROOT (S (NP (NNP Earth)) (VP (VBZ makes) (NP (DT a) (JJ complete) (NN revolution)) (NP (ADVP (IN around) (NP (DT the) (NN sun)) (PP (IN about) (ADVP (RB once)))) (DT every) (NN year))) (. .)))