( ( At ( the ( two equinoxes ) ) ) ( , ( ( the ( sub-solar latitude ) ) ( ( is ( ( 0 degrees ) ( which ( means ( that ( ( the Sun ) ( ( is directly ) ( overhead ( at ( the equator ) ) ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN At) (NP (DT the) (CD two) (NNS equinoxes))) (, ,) (NP (DT the) (JJ sub-solar) (NN latitude)) (VP (VBZ is) (NP (NP (CD 0) (NNS degrees)) (SBAR (WHNP (WDT which)) (S (VP (VBZ means) (SBAR (IN that) (S (NP (DT the) (NNP Sun)) (VP (VBZ is) (ADVP (RB directly)) (NP (NP (NN overhead)) (PP (IN at) (NP (DT the) (NN equator)))))))))))) (. .)))
At the two equinoxes, the sub-solar latitude is 0 degrees which means that the Sun is directly overhead at 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))) (. .)))