https://doi.org/10.1351/goldbook.A00267
Derivatives of oxoacids $\ce{R_{n}E(=O)OH}$ in which the hydroxy group is replaced by an amino group and the oxo group is replaced by $\ce{=NR}$. Amidines include carboxamidines, sulfinamidines and phosphinamidines, $\ce{R2P(=NR)NR2}$. In organic chemistry an unspecified amidine is commonly a carboxamidine.
See also: carboxamidines, sulfinamidines