seuil

Seuil is a French noun meaning boundary, limit, or edge between two spaces or states. It can be used literally for a doorway, figuratively for limits of ability, or as a boundary in various domains. The term originates in Old French seuil, with a long history in architecture and philosophy.

In architecture, a threshold is the strip of flooring at a doorway, often serving as a transition between rooms and sometimes acting as a barrier or seal against drafts.

In science and psychology, a threshold denotes a level at which a change becomes perceptible or a state is triggered. The absolute threshold is the minimum stimulus detectable half the time; the differential threshold (Just Noticeable Difference) is the smallest detectable change in stimulus. Thresholds vary by modality and context.

In medicine and environmental policy, a threshold dose is the smallest amount required to produce an effect; regulatory thresholds set limits for exposure, such as air or water quality standards. Ecological thresholds describe points where gradual change leads to abrupt ecological transitions.

In statistics and data processing, a threshold is a value used to separate categories or trigger an action, for example a probability threshold for classification or a signal-to-noise threshold in processing.