Complex sentence: In this sense, the energy of a system is said to be additive, and, for a homogeneous system in its own internal thermodynamic equilibrium, the internal energy is said to be an extensive quantity.
Split into simpler sentences: In this sense, the energy of a system is said to be additive. Likewise, for a homogeneous system in its own internal thermodynamic equilibrium, the internal energy is said to be an extensive quantity.