徳用

1. Origins, structure, and basic meaning

• Structure: 徳用 (とくよう) is a nominal modifier for a product size offering a large quantity for its price.
• Basic usage: 徳用の大きな袋 modifies a large economical bag for daily use, while 徳用サイズ forms a compound for the value-size format of detergent.

2. Common pitfalls and similar expressions

• Value relative to quantity, not price alone
  • 徳用 is tied to a large bag and family-size detergent in the examples. It should not be reduced to a mere discount; the sense concerns value from a larger quantity.