PDCA (Plan-Do-Check-Act) is the fundamental improvement cycle: plan a change with a hypothesis, carry it out on a small scale, check the result against the expectation, and act — standardise if it worked, adjust if not. The cycle repeats.
PDCA separates improvement from “let’s try something”: the Check step forces a measurement against an expectation, and the Act step forces a decision. Most organisations are strong in Plan and Do — and skip Check and Act. The result is activity without learning.
PDCA is the core of kaizen, A3 problem solving and ISO 9001’s requirement of continuous improvement.