|v. t.||1.||To bring or place under obligation, moral or legal; to hold by a constraining motive.|
|2.||To bind or firmly hold to an act; to compel; to constrain; to bind to any act of duty or courtesy by a formal pledge.|
|Verb||1.||obligate - force or compel somebody to do something; "We compel all students to fill out this form"|
|2.||obligate - commit in order to fulfill an obligation; "obligate money"|
|3.||obligate - bind by an obligation; cause to be indebted; "He's held by a contract"; "I'll hold you by your promise"|
|Adj.||1.||obligate - restricted to a particular condition of life; "an obligate anaerobe can survive only in the absence of OXYGen"|
facultative - able to exist under more than one set of conditions; "a facultative parasite can exist as a parasite or a saprophyte"