Obligately

Obligately is an adverb formed from the adjective obligate. It denotes that something is required by rule, necessity, or a specific constraint, rather than being optional. In general use, it emphasizes that an action or condition must occur or be true under given circumstances. It is most common in formal or scientific writing, where precision about necessity is important.

Etymology and usage notes: Obligately comes from the verb obligate, which traces to Latin obligatus, from obligare, meaning to bind or force. The adverbial form, like related words such as obligatorily or obligatoriness, conveys a sense of binding obligation or essential requirement. In everyday language, the term is less frequent, and speakers often substitute "necessarily," "required," or "compulsorily" depending on the context.

Biology and related technical usage: In biology, obligately is used to describe traits or relationships that are strictly required. For example, obligately anaerobic bacteria cannot survive in the presence of oxygen; obligately intracellular parasites must inhabit host cells to complete their life cycles. The term is often paired with adjectives (obligately aerobic, obligately parasitic, obligately marine) to convey that a condition is not optional for the organism.

See also: obligate, obligate parasite, obligate intracellular, facultative. The contrast between obligately and facultatively is common in scientific writing, where facultative indicates a capability that is optional or context-dependent rather than strictly necessary.