( Equinox ( ( is ( when ( ( the sun ) ( ( passes directly ) ( over ( the equator ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Equinox)) (VP (VBZ is) (SBAR (WHADVP (WRB when)) (S (NP (DT the) (NN sun)) (VP (VBZ passes) (ADVP (RB directly)) (PP (IN over) (NP (DT the) (NN equator))))))) (. .)))
Equinox is when the sun passes directly over the equator.
(ROOT (S (NP (DT The) (NN sun)) (VP (VBZ is) (ADVP (RB directly)) (PP (IN over) (NP (DT the) (NN equator))) (PP (IN during))) (. .)))