phototachometryn.

Origin: Formed within English, by compounding. Etymons: phototachometer n., -metry comb. form.

Etymology: < phototacho- (in phototachometer n.) + -metry comb. form. Compare slightly later tachometry n. at tachometer n. Derivatives.

rare. Apparently only attested in dictionaries or glossaries.

The measurement of the speed of light.

ΚΠ

1890 Cent. Dict. Phototachometry, the measurement of the velocity of light.

This entry has been updated (OED Third Edition, March 2006; most recently modified version published online June 2021).

单词	phototachometry
释义	phototachometryn. Origin: Formed within English, by compounding. Etymons: phototachometer n., -metry comb. form. Etymology: < phototacho- (in phototachometer n.) + -metry comb. form. Compare slightly later tachometry n. at tachometer n. Derivatives. rare. Apparently only attested in dictionaries or glossaries. The measurement of the speed of light. ΚΠ 1890 Cent. Dict. Phototachometry, the measurement of the velocity of light. This entry has been updated (OED Third Edition, March 2006; most recently modified version published online June 2021). < n.1890
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