蛍光灯

1. Origins, structure, and basic meaning

• Structure: 蛍光灯 (けいこうとう) is a fluorescent lamp or fixture. 蛍光灯が is the subject of a condition; 蛍光灯を is the object switched off.
• Basic usage: An old fluorescent light flickers intermittently; a room light is turned off before someone leaves.

2. Common pitfalls and similar expressions

• Light showing a fault and light operated by a person
  • が marks the fixture undergoing flicker; を marks it as an object of control. The noun refers to the lighting device rather than light as an abstract phenomenon.