The recently discovered order‐disorder transformations in pseudobinary semiconductor alloysAxB1−xCare shown to belong to a broader class of such transformations inAnB4−nC4semiconducting compounds (e.g., chalcopyrites, forn=2). Strain energy, set up by the atomic size mismatch between theA–CandB–Cbonds, is shown to control the nature of the state of order in chalcopyrites and pseudobinary alloys alike. These considerations lead to a classification of all bulk tetrahedral semiconductors into four classes of order‐disorder characteristics.