Waste in a process is any activity that does not result in moving the process closer to the final output or adding value to the final output.
The main wastes are seven (7W):
W1 – Overproduction;
W2 – Iventory;
W3 – Waiting;
W4 – Transportation;
W5 – Motion;
W6 – Process (useless steps in a process);
W7 – Defects.