The article introduces the concept of altern magnetism, a category of magnetic states that exhibit both collinear antiferromagnetic spins and alternating variations in local structures around these spins. This symmetry allows for typical ferromagnetic behaviors, such as non-zero net magnetic moments and the Anomalous Hall Effect (AHE). Altern magnets are categorized into three types: Type-I, Type-II, and Type-III. Type-I altern magnets exhibit ferromagnetic behaviors without external perturbations and belong to the ferromagnetic point group. Type-II and Type-III altern magnets can only show ferromagnetic behaviors under external perturbations, such as electric current or stress, which conserve parity-time-reversal (PT) symmetry. All types of altern magnets have broken PT symmetry. The concept of altern magnetism can be extended to include non-collinear spins and multiple local-structure variations. The article also discusses the magnetic anisotropy and the role of spin-orbit coupling in generating non-zero net magnetic moments. Various examples of altern magnets with different director and spin orientations are provided, and their magnetic properties are analyzed. The authors conclude that alternatism is a useful concept for understanding PT symmetry breaking and ferromagnetic-like behaviors in magnetic materials.The article introduces the concept of altern magnetism, a category of magnetic states that exhibit both collinear antiferromagnetic spins and alternating variations in local structures around these spins. This symmetry allows for typical ferromagnetic behaviors, such as non-zero net magnetic moments and the Anomalous Hall Effect (AHE). Altern magnets are categorized into three types: Type-I, Type-II, and Type-III. Type-I altern magnets exhibit ferromagnetic behaviors without external perturbations and belong to the ferromagnetic point group. Type-II and Type-III altern magnets can only show ferromagnetic behaviors under external perturbations, such as electric current or stress, which conserve parity-time-reversal (PT) symmetry. All types of altern magnets have broken PT symmetry. The concept of altern magnetism can be extended to include non-collinear spins and multiple local-structure variations. The article also discusses the magnetic anisotropy and the role of spin-orbit coupling in generating non-zero net magnetic moments. Various examples of altern magnets with different director and spin orientations are provided, and their magnetic properties are analyzed. The authors conclude that alternatism is a useful concept for understanding PT symmetry breaking and ferromagnetic-like behaviors in magnetic materials.