See Cryptographic module.
Sources:
NIST SP 800-133 Rev. 2 under Module

  The set of hardware, software, and/or firmware that implements approved security functions (including cryptographic algorithms and key generation) and is contained within a cryptographic boundary.
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NIST SP 800-175B Rev. 1 under Cryptographic module

  The set of hardware, software, and/or firmware that implements approved cryptographic functions (including key generation) that are contained within the cryptographic boundary of the module.
Sources:
NIST SP 800-57 Part 2 Rev.1 under Cryptographic module

  The set of hardware, software, and/or firmware that implements security functions (including cryptographic algorithms), holds plaintext keys and uses them for performing cryptographic operations, and is contained within a cryptographic module boundary. This Profile requires the use of a validated cryptographic module as specified in [FIPS 140].
Sources:
NIST SP 800-152 under Cryptographic module

  The set of hardware, software, and/or firmware that implements approved security functions and is contained within a cryptographic boundary.
Sources:
NIST SP 800-57 Part 1 Rev. 5 under Cryptographic module

  The set of hardware, software, and/or firmware that implements security functions (including cryptographic algorithms and keygeneration methods) and is contained within a cryptographic module boundary. See FIPS 140.
Sources:
NIST SP 800-133 Rev. 2 under Cryptographic module

  Program unit that is discrete and identifiable with respect to compiling, combining with other units, and loading.
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NIST SP 800-160v1r1

  Discrete and identifiable element with a well-defined interface and well-defined purpose or role whose effect is described as relations among inputs, outputs, and retained state.
Sources:
NIST SP 800-160v1r1 from ISO/IEC/IEEE 24765:2017

  an embedded software component of a product or application, or a complete product in-and-of-itself that has one or more capabilities.
Sources:
NISTIR 7511 Rev. 4 under Module