limiting factor

This term originates from ecology and biology, specifically referring to the resource that restricts the growth of an organism or population. In these scientific contexts, it describes a hard physical ceiling, such as the availability of phosphorus in a lake or sunlight in a forest.

In business and general productivity, the term is used as a metaphor for the "bottleneck." It identifies the single most critical constraint that, if removed, would allow for the most significant improvement in overall performance. It differs from a general "obstacle" by implying that this specific factor is the primary governor of the entire system's speed or scale.