Luminous

adj.calm, joyfulliterary

Meaning 1

Giving off or seeming to give off clear, gentle light.

Reach for it when describing a radiant object, color, face, or scene

A luminous moonlit path crossed the still water.

everyday
bright
high light level is all that needs saying
not when Bright lacks luminous's soft beauty and can imply glare.
warm
glowing
soft emitted or reflected light is the visual fact
not when Glowing can imply heat and is less elevated.
professional
luminescent
actual nonthermal light emission is technically established
not when Luminescent is narrower and unsuitable for a merely radiant face.
literary
radiant
light or happiness shines outward strongly
not when Radiant is often brighter and more expressive than luminous.

Exceptionally clear, insightful, or intellectually illuminating.

Reach for it when praising an explanation or mind in elevated prose

Her luminous essay connected the legal rule to ordinary family choices.

everyday
brilliant
exceptional intelligence or insight is supportable
not when Brilliant is stronger and may praise cleverness over clarity.
professional
lucid
clarity of explanation is the main merit
not when Lucid does not convey originality or intellectual radiance.
formal
illuminating
new understanding is produced for the reader
not when Illuminating describes the effect, not necessarily the work's own clarity.
literary
pellucid
rare elevated praise for crystal clarity fits
not when Pellucid is unfamiliar and can make the sentence less clear.

The definition and the example on this page are written here. The dictionaries above ground which meaning is being described, not the wording.