Manufacturing defect
Beginner
A flaw made while building a chip, like a speck of dust joining two wires or a wire that comes out broken.
Novice
A physical imperfection introduced while the chip is made: two wires shorted together, a wire broken open, missing or extra material, or a transistor too far off its intended size to work.
Expert
What test is really trying to catch. Fault models are logical stand-ins for defects, and coverage of a fault model only correlates with defect coverage. That gap is why teams add transition, bridging and cell-aware models on top of stuck-at.