obligate
1. ob.li.gate \'a:b-li-g*t, -l*-.ga-t\ aj 1: restricted to a particular mode of life {an ~ parasite} 2: ESSENTIAL, NECESSARY - ob.li.gate.ly av 2. ob.li.gate \'a:b-l*-.ga-t\ vt [L obligatus, pp. of obligare] 1a: to bind legally or morally : CONSTRAIN 1b: OBLIGE 2: to commit (as funds) to meet an obligation