From many verbs one can derive an agent noun for each gender:
- computare > computator (m), computatrix (f), computatrum (n)
- scribere > scriptor, scriptrix, scriptrum
Some of these derivatives are rarely found, but it is easy enough to derive productively when needed — when the perfect participle stem ends in a t. It is easy to speak about male and female lectureres, for example (lector and lectrix).
How to derive feminine an neuter agents from a verb whose perfect participle stem ends in an s? The masculine derivative is common and easy (e.g. profiteri > professor), but how to form the feminine and neuter versions? I would like this to be analogous with the derivatives for computare and scribere above, so using the present participle (eg. profitens) is unsatisfactory.
If you can give a way to derive feminine and neuter agents, please give actual use examples. Examples should preferably be classical. If there are no classical examples, are there later ones and did ancient grammarians notice that such words are missing?
Here is a feeble attempt to derive in feminine and neuter: The stem of profiteri is profit- and when we add a t for perfect participle, we get profitt- which has turned into profett- and then profess-. It seems easier to derive before making the subsitution tt > ss. The companions of profettor would then be profettrix and profettrum. Intervocalic tt should become ss, but it feels more natural to take ttr > tr. This leaves me with professor, profetrix and profetrum. This is my best guess, but I have no idea if this is consistent with classical (or any other) use of Latin.