Limits of the spatial extensions of the model - flow- or mass/heat transport- conditioning sections or points (see boundary conditions below).

A boundary is a verbal communication that sets limits on what we accept or tolerate from others. That includes how others treat us…..how they speak to us……what we’ll give to them or what we'll accept from them. Boundaries are lines that draw and define ourselves. Boundaries teach others how to treat us.

the spatial and temporal conditions and practical constraints under which environmental data are collected. Boundaries specify the area or volume (spatial boundary) and the time period (temporal boundary) to which the decision will apply. Samples are then collected within these boundaries.

A limit, a bound, anything marking a limit.