What does calm or light wind indicate in terms of speed classification?

Calm or light wind is typically classified as having speeds below 5 knots. This classification reflects very gentle breezes where wind speeds are minimal, often leading to conditions where smoke rises vertically and leaves are still. The designation of calm or light wind is significant in meteorological observations, as it can impact weather patterns, air pollution dispersion, and various outdoor activities.

The other classifications mentioned in the question, such as moderate winds and strong winds, would clearly fall outside this threshold, with moderate winds being generally around 10 knots. Variability in wind speeds suggests fluctuations, which does not align with the consistent low speeds that characterize calm or light wind conditions. Hence, the correct interpretation of calm or light wind directly relates to speeds under 5 knots, which is why this classification is widely recognized in meteorological practices.