Inverse function - a mathematical function giving temperature as a function of voltage.  The thermocouple reference functions cannot be inverted exactly with a finite number of coefficients; consequently the inverse functions are only approximate, to within the errors stated in the tables of coefficients.

Inverse function coefficients, or inverse coefficients - the numerical parameters used in the inverse functions.  Polynomial coefficients are denoted d_i for the ith power of thermoelectric voltage.

Measurement junction - that junction of dissimilar metals in a thermoelectric circuit that is placed at the location of the unknown temperature that is to be determined.

Reference function - the mathematical function giving the thermoelectric voltage as a function of temperature.  This function defines the response of a specific letter-designated thermocouple type.

Reference function coefficients, or coefficients - the numerical parameters used in the reference functions. Polynomial coefficients are denoted c_i for the ith power of temperature.  For type K, there are additional coefficients a₀, a₁, and a₂. For type K, there are additional coefficients a₀, a₁, and a₂.

Reference junctions - those junctions in a thermoelectric circuit that are maintained at a fixed, known temperature, which is often 0 °C.

Thermocouple - a pair of dissimilar electrical conductors joined at one end (the measuring junction).  When the other ends of the thermocouple are maintained at a known reference temperature, the thermoelectric voltage produced by the thermocouple is a repeatable function of the temperature of the measuring junction.

Electromotive force (EMF) - the thermoelectric voltage induced by the temperature gradient along two dissimilar electrical conductors.

Thermoelectric voltage - also called Electromotive Force (EMF).