粘液

1. Origins, structure, and basic meaning

• Structure: 粘液 (ねんえき) is a noun for a sticky fluid secreted on an organism’s surface or within its body.
• Basic usage: 透明な粘液で覆われる identifies the substance coating a fish, while 鼻の粘液には働きがある makes nasal mucus the topic with a particle-trapping function.

2. Common pitfalls and similar expressions

• Coating substance and physiological function
  • 粘液で覆う uses で for the coating material, while 粘液には marks the substance as topic of a function. Being transparent does not mean it lacks viscosity like water.