Delight is as the flight,
ratio
Mathematical term—Dickinson frames delight as a calculable proportion. The irony: you can't measure joy like the schools measure things.
skein
A coiled bundle of yarn. The rainbow isn't arched—it's tangled thread thrown across the sky, temporary and messy.
aliment
Food, nourishment. Flight feeds you; rainbows only look pretty. Delight has to sustain, not just dazzle.
bent stripe
She refuses 'rainbow'—calls it a bent stripe. Child's-eye view: before you learn the poetic word, you see the thing itself.
eccentricity
The child thinks empty skies are weird and rainbows are normal. Delight as the default state—adulthood reverses this.
cheat the sight
Butterflies vanish mid-flight. 'Cheat' implies betrayal—beauty owes us nothing but we feel robbed when it leaves.
dower latitudes
Dower: a widow's inheritance. The butterflies will give their beauty to distant places, leaving us nothing.
fashion
Double meaning: manner/style, but also the cutting and shaping of cloth. Our portion of delight is cut short, the pattern complete.