Collateral (lat. collateralis - lateral) is a concept used in different areas, but has a general meaning.
In medicine, collateral vessels are additional blood vessels that connect the main arteries and provide blood supply to organs and tissues when the main vessels are narrowed or blocked. The development of collaterals helps compensate for the lack of blood flow.
In finance, collateral is assets pledged to secure a loan. This could be real estate, securities, equipment. Collateral serves as a guarantee of loan repayment.
In military affairs, collateral damage is accidental, unintentional damage to civilians and objects caused during military operations.
Thus, in different spheres, collateral means an additional, secondary, accompanying object, phenomenon or consequence in relation to the main one.