Decreased size of the teeth, which can be defined as a mesiodistal tooth diameter (width) more than 2 SD below mean. Alternatively, an apparently decreased maximum width of tooth. The phenotype is Microdontia (Human Phenotype Ontology id HP_0000691). Also known as: Decreased size of tooth, Decreased width of tooth, Small teeth, Small tooth, Tooth hypoplasia, Tooth hypotrophy, Underdeveloped tooth.