Requirements levied on an information system that are derived from applicable laws, Executive Orders, directives, policies, standards, instructions, regulations, or procedures, or organizational mission/business case needs to ensure the confidentiality, integrity, and availability of the information being processed, stored, or transmitted.
Sources:
FIPS 200 under SECURITY REQUIREMENTS

  Requirements levied on an information system that are derived from applicable laws, Executive Orders, directives, policies, standards, instructions, regulations, procedures, or organizational mission/business case needs to ensure the confidentiality, integrity, and availability of the information being processed, stored, or transmitted.
Sources:
NIST SP 800-137 under Security Requirements from FIPS 200
NIST SP 800-30 Rev. 1 under Security Requirements from FIPS 200
NIST SP 800-39 under Security Requirements from FIPS 200

  A requirement that specifies the functional, assurance, and strength characteristics for a mechanism, system, or system element.
Sources:
NIST SP 800-160 Vol. 2 Rev. 1

  A requirement levied on an information system or an organization that is derived from applicable laws, executive orders, directives, policies, standards, instructions, regulations, procedures, and/or mission/business needs to ensure the confidentiality, integrity, and availability of information that is being processed, stored, or transmitted. Note: Security requirements can be used in a variety of contects from high-level policy activies to low-level implementation activities in system development and engineering disciplines.
Sources:
NIST SP 800-37 Rev. 2 from FIPS 200 - adapted

  A requirement levied on an information system or an organization that is derived from applicable laws, executive orders, directives, regulations, policies, standards, procedures, or mission/business needs to ensure the confidentiality, integrity, and availability of information that is being processed, stored, or transmitted.
Sources:
NIST SP 800-53 Rev. 5 from FIPS 200 - Adapted
NIST SP 800-53A Rev. 5 from FIPS 200 - Adapted
NIST SP 800-53B from FIPS 200 - Adapted

  A requirement that has security relevance.
Sources:
NIST SP 800-160v1r1

  A requirement levied on a system or an organization that is derived from applicable laws, Executive Orders, directives, regulations, policies, standards, procedures, or mission/business needs to ensure the confidentiality, integrity, and availability of information that is being processed, stored, or transmitted.
Sources:
NIST SP 800-171r3 from FIPS 200 - adapted, NIST SP 800-53 Rev. 5 - adapted