Tania stared at him aghast, unable to speak,請問aghast是形容詞,文法上如何解釋,另He stood aghast at the sight of so much blood中 aghast文法上如何解釋?

aghast, adj--used not before a noun, but after it;----a feeling or looking shocked(=aghast) by someone(=kwangkwo) you have seen or just found out (=a bloody body)
eg:-He stood aghast=He was aghast
----He stood aghast at the sight of so much blood on Tania's bloody dead body(just found out !)
eg:-Kwangkwo looked aghast at her (=Tania) dead bloody body; (just found out)----a linking verb as an adj. not before noun; but after proper noun=Kwangkwo.

aghast在此是作為「主格補語」(subjective complement)，以補述主詞意義。

主格補語通常為名詞，形容詞或其相等語。
「不完全不及物動詞」也稱為「聯繫動詞」(linking verb), be以外的聯繫動詞常以名詞或形容詞為補語。
如：He stood still.
It grows dark.
The music sounds sweet.

請參見柯旗化《新英文法》pp.216~221