The Allen and Greenough is still under construction;
so some links may not work quite the way you would expect.
271. The Subject of a sentence is usually a Noun or
Pronoun, or some word or group of words used as a Noun: -
- equites ad Caesarem
venerunt, the cavalry came to Caesar.
- humanum est errare, to err
- quaeritur cum mors malum sit,
the question is whether death is an evil.
a. But in Latin the subject is often
implied in the termination of the verb: -
- sede-mus, we sit.
- curri-tis, you run.
- inqui-t, says he.