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.