光線|こうせんkousen[0]heiban (flat)

1. nounray (of light); beam; light
   このランプは強つよい光線こうせんを出だす。↗

   This lamp sends out a powerful beam.

• Synonym光ひかりNeutralThe everyday word for light or brightness, also used figuratively for hope; 「光線」 focuses on light as a line or ray.
• SynonymビームNeutralLoanword for a concentrated beam of light, common in sci-fi and laser contexts.
• Synonym光芒こうぼうWrittenWritten/formal prose for rays of light radiating out, with a literary flavor.
• Synonym光束こうそくWrittenWritten/formal prose for light gathered into a bundle, or luminous flux in physics; academic.
• Related可視光かしこうWrittenWritten/formal prose term for light in the wavelengths the human eye can see; a physics word, narrower in scope than 「光線」.
• Antonym暗闇くらやみNeutralTotal darkness, a place with no light; the opposite of 「光線」.

Use 「光線」 for light as a line or ray, as in 「光線が強い」. In everyday speech say 「光」; for laser beams 「ビーム」; for visible light in physics 「可視光」. 「暗闇」 is the opposite: darkness.

Usage comparisons are AI-assisted and cross-checked by multiple models; for study reference only

1. 光ひかりが進すすむ経路けいろを示しめす線せん。