( ( ( ( Embryogenesis ( covers ( ( the ( first ( eight weeks ) ) ) ( of development ) ) ) ) and ) ( ( at ( ( the beginning ) ( of ( the ( ninth week ) ) ) ) ) ( ( the embryo ) ( is ( termed ( a fetus ) ) ) ) ) ) . )
(ROOT (S (S (NP (NNS Embryogenesis)) (VP (VBZ covers) (NP (NP (DT the) (JJ first) (CD eight) (NNS weeks)) (PP (IN of) (NP (NN development)))))) (CC and) (S (PP (IN at) (NP (NP (DT the) (NN beginning)) (PP (IN of) (NP (DT the) (JJ ninth) (NN week))))) (NP (DT the) (NN embryo)) (VP (VBZ is) (VP (VBN termed) (NP (DT a) (NN fetus))))) (. .)))
Embryogenesis covers the first eight weeks of development and at the beginning of the ninth week the embryo is termed a fetus.
(ROOT (S (NP (NP (DT The) (NN development)) (PP (IN of) (NP (NP (DT the) (JJ respiratory) (NN system)) (PP (IN in) (NP (DT the) (NN fetus)))))) (VP (VBZ begins) (PP (IN at) (NP (QP (RB about) (CD 4)) (NNS weeks)))) (. .)))
The development of the respiratory system in the fetus begins at about 4 weeks.