The correct answer is D) distance between corresponding points on adjacent threads. The 'pitch' in the American National Screw Thread nomenclature refers to the distance between corresponding points on adjacent threads, such as the crest of one thread to the crest of the next thread. This is the fundamental measurement that defines the spacing of the threads on the screw. The other answer choices are incorrect because they describe different characteristics of the screw thread, such as the angle of the thread (B and C), or the ratio of threads to length (A), but do not specifically define the 'pitch' as the distance between adjacent threads.