How many letters does the top answer for “another word for luminousness” have?

The most common answer is luminance (9 letters).

Crossword clue: another word for luminousness

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

luminance 9 letters gen-syn

the quality of being luminous; emitting or reflecting light

luminosity 10 letters gen-syn

the quality of being luminous; emitting or reflecting light

another word for about 50% similar → approximately, roughly, some

another word for terms 50% similar → footing

another word for under 50% similar → nether

another word for word 50% similar → phrase