What unit is used to express conductor sizes larger than 4/0 AWG?

The unit used to express conductor sizes larger than 4/0 AWG is called kcmil, which stands for "thousand circular mils." This measurement is commonly used in the electrical industry for large conductors, as it provides a straightforward way to quantify the cross-sectional area of the wire. The kcmil designation specifically helps in simplifying the understanding of wire sizes, particularly for electricians and engineers dealing with larger gauge conductors.

While MCM also refers to thousand circular mils, the use of kcmil has become more standardized in modern practices. Both kcmil and MCM can be technically correct in some contexts, but kcmil is the preferred term in contemporary electrical applications. The other options such as MM2, which refers to square millimeters, and AWG+, which suggests a continuation of the American Wire Gauge system, do not apply to the indicated wire sizes larger than 4/0 AWG.