compulsory
adj.
1580s, from Medieval Latin compulsorius, from Latin compulsus, past participle of compellere "to drive together, force, compel" (see compel).
〔李〕[compuls =tocompel强迫；-ory ⇒“characterized by compelling or being compelled带有强迫性质的”→] a. com-pelling；compelled or required强迫的，强制的；必需的，义务的