essentiality

Essentiality is the quality or state of being essential or absolutely necessary for a particular outcome, function, or survival. In biology, essentiality commonly refers to genes, metabolic reactions, or nutrients required for an organism’s viability under specific conditions. A gene is considered essential if its loss prevents growth or survival. Essentiality is often determined experimentally by gene knockout, knockdown, or CRISPR disruption, and it can be context-dependent: a gene may be essential in one environment but not another, at a certain developmental stage, or in a particular genetic background. Computational models that simulate growth can identify essential genes in silico, and the concept of synthetic lethality describes situations where two nonessential genes together are lethal.

In metabolism, essential nutrients are substances that organisms cannot synthesize in sufficient amounts and must obtain from the diet. In humans, these include certain amino acids, fatty acids, vitamins, and minerals. In ecology, essential functions or keystone processes maintain ecosystem structure, and the removal of certain species can have disproportionate effects on community stability and function.

In philosophy, essentialism is the view that objects have essences—immutable properties that define their identity—distinct from contingent attributes.

Significance: understanding essentiality helps identify targets for antimicrobial or cancer therapies, informs nutrition and dietary guidelines, and supports studies of genome design and ecosystem management. It is a context-dependent concept, often viewed as a spectrum rather than a strict binary.