Definition
A bottleneck is the narrowest part of a system — the stage, resource, or step that limits how much can flow through the whole. Just as the neck of a bottle dictates how fast liquid pours out regardless of how wide the body is, the slowest or scarcest element sets the pace for everything downstream.
The term applies far beyond physical pipes. In a factory, the bottleneck is the machine with the longest queue. In a team, it may be the one person whose approval everything waits on. In an argument, it may be a single unresolved assumption. Wherever throughput matters, there is almost always one constraint doing the limiting.
Why it matters
How it works
The leverage of the bottleneck idea is that it concentrates attention. A system has many parts, but only one of them caps its performance at any moment. Effort spent anywhere else is wasted at the margin — speeding up a non-constraint simply produces work that waits longer at the real choke point.
The disciplined response is to locate the constraint, protect it from idleness or interruption, and subordinate the rest of the system to its pace. When the constraint is finally widened, performance jumps until a new part becomes limiting. Progress, viewed this way, is a sequence of bottlenecks identified and broken — not a uniform push on everything at once.