Airy, Aerial and Ethereal can all mean as light and insubstantial as air.
Airy seldom suggests a transcendent quality; in its widest sense it implies little more than immateriality.
- the poet’s pen . . . gives to airy nothing a local habitation and a name
When applied to persons, their words, or their manners, it may imply an affectation of grandeur or putting on airs mere affectation of nonchalance.
- replied with airy condescension
- airy refusal to take good advice
When used of motion or movements, it suggests lightness and buoyancy.
- the slight harebell raised its head, elastic from her airy tread
Aerial in figurative use is found chiefly in poetry where it usually connotes impalpability, extraordinary delicacy, or elusiveness, and is applied to things rather than to persons.
- mountains … fair of aspect, with aerial softness clad
- the aerial hue of fountain-gazing rases
- fine and aerial distinctions
Ethereal implies not the atmosphere surrounding the earth but the rarefied air once believed to fill the heavenly regions and so imputes a celestial or supramundane character to the person or thing it qualifies. Sometimes it suggests an unearthly translucency.
- fire . . . without heat, flickering a red gold flame . . . ethereal and insubstantial
so . . . ethereal in appearance with its cloud colors, that . . . even . . . the most beautiful golden shades . . . seemed heavy and dull and dead-looking by comparison
Sometimes, especially when referred to persons, their words, or their thoughts, it suggests disembodied spirit or apartness from material interests.
- the ethereal quality of Shelley’s poetry
- at times he tends to fall into excessive subtlety, to be too vaporous and ethereal