( ( ( The ( closest point ) ) ( of ( ( ( a ( celestial ( body 's ) ) ) orbit ) ( to ( the Sun ) ) ) ) ) ( ( is ( known ( as ( the perihelion ) ) ) ) ; ) )
(ROOT (S (NP (NP (DT The) (JJS closest) (NN point)) (PP (IN of) (NP (NP (NP (DT a) (JJ celestial) (NN body) (POS 's)) (NN orbit)) (PP (TO to) (NP (DT the) (NNP Sun)))))) (VP (VBZ is) (VP (VBN known) (PP (IN as) (NP (DT the) (NN perihelion))))) (: ;)))
The closest point of a celestial body's orbit to the Sun is known as the perihelion;
(ROOT (S (NP (DT The) (NNS planets)) (VP (VB orbit) (PRT (RP around)) (NP (DT the) (NN sun))) (. .)))