Moho

This term is a specialized geological shorthand derived from the name of Andrija Mohorovičić, the Croatian seismologist who discovered the boundary. In professional academic writing, it is often capitalized as "Moho" to honor the proper name, though it is frequently treated as a common noun in general scientific discourse.

Because it refers to a unique, singular planetary boundary, the term is used exclusively in the singular. It describes a specific discontinuity in seismic velocity rather than a repeatable object or a substance.