obligate

Obligate is an English adjective used to describe something that must be done, endured, or accepted; it denotes a binding requirement within a system or framework. The word can also function as a verb, meaning to bind by obligation or to commit someone or something to a required condition.

Etymology: Obligate comes from the Latin obligatus, the past participle of obligare, meaning to bind or compel.

In biology and ecology, the term denotes a dependence that is absolute or essential for survival or reproduction. An obligate parasite relies on a host for all or most of its life cycle. An obligate intracellular parasite cannot reproduce outside a host cell. An obligate aerobe requires oxygen to grow, while an obligate anaerobe is harmed by oxygen. An obligate mutualist depends on its partner for survival and cannot complete its life cycle independently. The concept is frequently contrasted with facultative, which describes organisms or interactions that can use a given condition but do not require it and can survive in a broader range of environments.

In nonbiological contexts, obligate describes duties, requirements, or conditions that are legally or morally binding or mandated by rules, regulations, or professional codes. For example, certain roles or processes may be described as obligate within an organization or field, meaning they must be performed or fulfilled.

See also: facultative, obligate parasite, obligate aerobe, obligate anaerobe, obligate mutualist.