potestās

Potentia, potentatus, and potestas (πότνιος) denote an exterior power, which acts by means of men, and upon men; whereas vis and robur denote an interior power and strength, independent of the co-operation and good-will of others. Potentia denotes a merely factitious power, which can be exerted at will, like δύναμις; potentatus, the exterior rank of the ruler, which is acknowledged by those who are subject to him, like δυναστεία; potestas, a just and lawful power, with which a person is entrusted, like ἐξουσία. Tac. Ann. xiii. 19. Nihil tam fluxum est quam fama potentiæ non sua vi nixæ. Vis (ἴς) is the strength which shows itself in moving and attacking, as an ability to constrain others, like κράτος; robur (from ἐῤῥῶσθαι) the strength which shows itself in remaining quiet, as an ability to resist attack, and remain firm, like ῥώμη. (v. 83.)

Occasio and opportunitas are the opportunities which fortune and chance offer; occasio, the opportunity to undertake something in a general sense, like καιρός; opportunitas, the opportunity to undertake something with facility and the probability of success, like εὐκαιρία; whereas potestas and copia are opportunities offered by men, and through their complaisance; potestas denotes the possibility of doing something with legal authority; copia the possibility of doing something with convenience; lastly, facultas, as the most general expression, the possibility to do something in a general sense.