Pulmonalis or Pulmonaris? It's Elementarius, My Dear Watson

The adjectival suffix -alis and its allomorph -aris are very common in the anatomical nomenclature; however, rules governing differential usage, such as -aris substituting for -alis following an -l-, leave many exceptions. Here, we report an empirical study of 985 adjectives with -alis and -aris suffixes used in Terminologia Anatomica (2nd ed.) and Terminologia Histologica to develop phonological rules that would have fewer exceptions. As a general rule, the default is -alis, but -aris after -l-, except with -r- between. This tripartite rule reduces the exceptions to < 10%, but this can be reduced to < 6% by limiting the distance over which the dissimilation effect of an -l- in the base is expected to operate. After consideration of precedents in classical, late, and medieval Latin, and derivatives in modern Romance and Germanic languages, we recommend the use of pulmonarius, elementarius, unitarius, pulparis, and lumbaris, and compound adjectives created from these words, in place of related adjectival forms that were previously used in anatomical Latin.