A world resembling Earth which coexists with Earth in another dimensional space.
In general, any world other than the Earth. To be more precise, an alternate Earth is separated from other Earths by its unique vibrational frequency. In this sense, alternate Earths are considered different from parallel dimensions and hypertimelines.
A world resembling Earth in physical characteristics, natural phenomena, life forms, and, to some extent, history, which exists in the equivalent space to Earth's in another dimension. An alternate Earth may either be a divergent Earth or a parallel Earth.