x tooth_number N if and only if (i) x is a tooth, and (ii) x is ancestrally tooth number N in a series of teeth repeated along an anterior-posterior axis, typically on the lateral side of a structure such as a jaw, with tooth_number 1 being the anteriormost. Note that this count refers to the total number of teeth starting from the first, regardless of the type of tooth. If sub-systems are required for numbering within a series of teeth of the same type, consider a subproperty. For example, in a human, maxillary canine = tooth 3 of upper jaw = canine_tooth 1 of upper jaw.