[f. TURNING vbl. sb. + POINT sb.]
1. lit. A point at which something turns, or changes its direction of motion, etc.; spec. a maximum or minimum point on a graph, where it begins to tend downwards or upwards.
1856. Stanley, Sinai & Pal., xii. 400. Near what may be called the turning point of its course, where its spacious stream is diverted … by the chain of Amanus.
2. fig. A point at which a decisive change of any kind takes place; a critical point, crisis. (The usual sense.)
1822. Hartford Courant, 19 Feb., 1/5. With regard to the Russian monarchy, who may be now politically speaking, styled the turning point in the destiny of Europe, his steps appear to be dark, mysterious, and inscrutable.
1851. Ruskin, Arrows of Chace (1880), I. 86. I believe these young artists to be … at a turning-point, from which they may either sink into nothingness or rise to very real greatness.
1874. Parker, Illustr. Goth. Archit., I. iii. 92. At this principal turning-point in the history of architecture.
1885. Athenæum, 23 May, 669/1. The turning point from summer to autumnal weather.
1887. J. C. Morison, Service of Man, 8. One of those turning-points in the evolution of thought which mark the close of an old epoch.
3. Surveying. A subsidiary bench-mark whose height above datum is determined during the operation of finding, by differential levelling, the difference of level of two permanent bench-marks.
So called because the graduated staff on which the height is read off is at this point turned round so as to be read from the permanent (or the next subsidiary) bench-mark.
1891. in Cent. Dict.
