Amidst means in the middle of, in formal use. Amidst the ruins, amidst growing concern, amidst it all.
It is the same word as amid with an added -t and is slightly more literary, which is the only difference — no rule distinguishes them and both are correct. It is commoner in British writing than American. Note amongst and whilst, which took the same excrescent -t; and that the -st ending gives all three a faintly old-fashioned air.
1prepositionamidstIn the middle of, in formal use.
“The old chapel stood amidst the ruins of the abbey.”
amidst is a preposition of position.
Amidst is amid plus an adverbial -s and then an excrescent -t, from Old English on middan. Amongst and whilst grew their final t the same way.
Old English
on
Middle English
amidde
English, today
amidst
Built from
From amids + t, from amid + s. by surface analysis, amid + -st. Root amid from Middle English amidde, amiddes, on midden, from Old English on middan (“in the middle”), from midd (“central”) (English mid).
Etymology from Wiktionary, CC BY-SA