Alternagnetism is a magnetic state characterized by collinear antiferromagnetic spins and alternating local structures around spins, allowing ferromagnetic behaviors. Type-I alternagnets exhibit ferromagnetic behaviors without external perturbations and belong to the ferromagnetic point group. Type-II and Type-III alternagnets require external perturbations (e.g., electric current, stress) to show ferromagnetic behaviors, and all alternagnets have broken PT symmetry. Alternagnetism can be extended to include non-collinear spins and multiple local-structure variations. Alternagnets are classified based on their magnetic point groups (MPGs). Type-I alternagnets have non-zero net magnetic moments and exhibit ferromagnetic behaviors. Type-II alternagnets have zero net magnetic moment and require external perturbations to show ferromagnetic behaviors. Type-III alternagnets also have zero net magnetic moment and do not exhibit odd-order AHE. All alternagnets have broken PT symmetry, and their magnetic behaviors are influenced by spin-orbit coupling and local structural variations. Type-I alternagnets, such as those with m/m'm-type MPGs, exhibit linear AHE and are weak ferromagnets. Type-II alternagnets, like those with 4/mm/m-type MPGs, can exhibit high-odd-order AHE under PT-symmetric perturbations. Type-III alternagnets, such as those with mmm-type MPGs, do not exhibit odd-order AHE but can show other spin-related phenomena like diagonal odd-order current-induced magnetization. Alternagnetism encompasses various spin configurations, including non-collinear spins and multiple director orientations. Examples include magnetic states in materials like Mn3Ge, CoF2, and others. Alternagnets can exhibit ferromagnetic-like behaviors under specific conditions, such as applied current or stress, and their properties are influenced by symmetry and spin-orbit coupling. The study highlights the importance of symmetry in understanding alternagnetism and its potential applications in spintronics. Alternagnets offer a unique opportunity to leverage the advantages of both ferromagnetism and antiferromagnetism, with potential applications in spin-based devices and materials with novel magnetic properties.Alternagnetism is a magnetic state characterized by collinear antiferromagnetic spins and alternating local structures around spins, allowing ferromagnetic behaviors. Type-I alternagnets exhibit ferromagnetic behaviors without external perturbations and belong to the ferromagnetic point group. Type-II and Type-III alternagnets require external perturbations (e.g., electric current, stress) to show ferromagnetic behaviors, and all alternagnets have broken PT symmetry. Alternagnetism can be extended to include non-collinear spins and multiple local-structure variations. Alternagnets are classified based on their magnetic point groups (MPGs). Type-I alternagnets have non-zero net magnetic moments and exhibit ferromagnetic behaviors. Type-II alternagnets have zero net magnetic moment and require external perturbations to show ferromagnetic behaviors. Type-III alternagnets also have zero net magnetic moment and do not exhibit odd-order AHE. All alternagnets have broken PT symmetry, and their magnetic behaviors are influenced by spin-orbit coupling and local structural variations. Type-I alternagnets, such as those with m/m'm-type MPGs, exhibit linear AHE and are weak ferromagnets. Type-II alternagnets, like those with 4/mm/m-type MPGs, can exhibit high-odd-order AHE under PT-symmetric perturbations. Type-III alternagnets, such as those with mmm-type MPGs, do not exhibit odd-order AHE but can show other spin-related phenomena like diagonal odd-order current-induced magnetization. Alternagnetism encompasses various spin configurations, including non-collinear spins and multiple director orientations. Examples include magnetic states in materials like Mn3Ge, CoF2, and others. Alternagnets can exhibit ferromagnetic-like behaviors under specific conditions, such as applied current or stress, and their properties are influenced by symmetry and spin-orbit coupling. The study highlights the importance of symmetry in understanding alternagnetism and its potential applications in spintronics. Alternagnets offer a unique opportunity to leverage the advantages of both ferromagnetism and antiferromagnetism, with potential applications in spin-based devices and materials with novel magnetic properties.