Recycling is the re-use of materials that would otherwise be considered waste. Those materials can be sources from pre-consumer waste (materials used in manufacturing) or post-consumer waste (materials discarded by the consumer).

In theory, recycling would be a continuing reuse of materials for the same purpose, but in practice much recycling extends the useful life of a material, but in a less versatile form. For example, as paper is recycled, the fibers shorten, making it less useful for higher grade papers. Other materials can suffer from contamination, making them unsuitable for food packaging.

Articles about, or including aspects of, recycling:

• Autonomous building
• Resin identification code
• Ship-Submarine recycling program