The correlation between growth twinning and crystalline reorientation of faceted growth materials during directional solidification was demonstrated through matrix calculation and Thompson regular tetrahedron model diagrams. The correlation is that the crystalline reorientation results from the mirror symmetry operation of initial orientation on different twin planes. In total, seven possibilities of crystalline reorientation caused by single-twinning from ⟨110⟩, ⟨111⟩, and ⟨112⟩ initial axial orientation were predicted, four of which were verified experimentally in the representative Tb 0.3 Dy 0.7 Fe 2 alloys. G rowth twinning (GT) has attracted much attention owing to its effects on the growth pattern, microstructure, crystalline orientation, and thus the property. The effects of GT on crystal growth were first discovered from Ge in the 1950s 1 and has been extensively observed in metals, intermetallic compounds, semiconductors, and oxides, especially for the faceted growth materials with a large entropy of melting, for instance, Ge, 1−4 Si, 5−13 AlSi, 14−19 and TbDyFe. 20−25 Growth with GT is usually a major growth pattern for the faceted growth materials because twinning grooves can reduce the growth supercooling degree.Remarkable property anisotropy exists in almost all faceted growth materials. The excellent properties usually appear along specific crystalline orientation. For example, the magnetostriction along ⟨111⟩ orientation (λ 111 ) is about 20 times of that along ⟨100⟩ orientation (λ 100 ) in TbDyFe giant magnetostrictive alloys. 26 Thus, the control of crystalline orientation along certain direction is of crucial importance for faceted growth materials.However, the phenomenon that the crystalline orientation can be changed by GT is frequently observed in faceted growth materials. 14,24,27 Especially for directional solidification process, the axial orientation is usually changed even with a single crystal seed. For instance, it is observed that the axial orientation changes from ⟨110⟩ initial axial orientation to ⟨114⟩ in TbDyFe alloys, 23,24 and a two-{111}-twin system growth model is proposed. 24 However, because of lacking systematic theoretical analysis, the correlation between GT and crystalline reorientation remains still unclear. Investigating all possibilities of reorientation from different initial axial orientations could provide a better understanding for crystalline orientation control and properties.In this communication, we analyzed the correlation between GT and reoriented growth from ⟨110⟩, ⟨111⟩, and ⟨112⟩ initial axial orientations in faceted growth materials with facecentered-cubic (fcc) structure. All the possibilities of crystalline reorientation from these three orientations were calculated by matrix and intuitively shown through a Thompson regular tetrahedron model, and the results were confirmed experimentally in a representative alloy of Tb 0.3 Dy 0.7 Fe 2 .High-purity starting element terbium, dysprosium, and iron with a purity level of 99.99% were remelted four times by ar...