酸素

1. Origins, structure, and basic meaning

• Structure: 酸素, read さんそ, is the substance noun oxygen.
• Basic usage: 水中の酸素を測る measures oxygen in water; 多くの酸素を必要とする describes the body's increased need during exercise.

2. Common pitfalls and similar expressions

• Measured and physiologically required oxygen
  • 酸素 may be measured as a substance in air or water, or discussed as what an organism needs for respiration. Context determines whether the focus is concentration or required amount.