That which is required for continued existence or function.
Blood that is needed for continued life; blood regarded as the seat of life.
The essential or innate characteristics of a person or thing which will always tend to manifest, especially in contrast to specific contexts, reason, religious duty, upbringing, and personal pretense or effort.
Spontaneous love, affection, or reverence, especially between parent and child.
The need to urinate and defecate.
The distinguishing characteristic of a person or thing, understood as its general class, sort, type, etc.
Sexual desire.
The way things are, the totality of all things in the physical universe and their order, especially the physical world in contrast to spiritual realms and flora and fauna as distinct from human conventions, art, and technology.
The vital functions or strength of someone or something, especially (now dialect) as requiring nourishment or careful maintenance or (medicine) as a force of regeneration without special treatment.