Foreign matter

The term foreign matter is used in different contexts but with a similar meaning:

• in medicine it means either
  • As part of the blood, a substance ( pathogens , poisons ) that certain lymphocytes recognize and fight as foreign, see antigen
  • a substance within cells that was not produced by the metabolism, see xenobiotic
• In the food sector , it identifies unusual ingredients that can, however, intentionally or unintentionally become food components, see preservatives , pesticides
• In metallurgy , this refers to the impurities in metals and alloys that are not involved in the crystal structure , which remain in the melt after their production and are reduced to around 0.1% by mass with economic technical measures.
• In the field of construction, these are substances in aggregates that are of foreign origin (such as building rubble, metals and plastics)

This is a disambiguation page for differentiating between several terms identified with the same word.