1. An antiphase boundary (APB) is defined as a boundary that separates two regions of the same ordered phase, resulting from symmetry breaking during ordering processes. It occurs when two regions with wrong compositional bonds across the interface come into contact. (ScienceDirect, AI generated definition based on: Physical Metallurgy (Fifth Edition), 2014). 2. An antiphase boundary refers to the contact between regions in a crystal that have undergone a phase transformation and differ from each other by a specific orientational relationship. These boundaries occur when a mineral transforms from a high-symmetry structure to a lower-symmetry structure, resulting in the loss of translational symmetry. (ScienceDirect, AI generated definition based on: Encyclopedia of Physical Science and Technology (Third Edition), 2003).