קָעוּר (ka'ur) — concave
Etymology
The word קָעוּר was coined by Prof. Aryeh Feigenbaum, one of the most prolific creators of modern Hebrew vocabulary, in his 1927 nursing textbook published by Hadassah: "The Eye: Its Diseases, Health Maintenance, and Treatment." Feigenbaum coined the word specifically to fill a terminological gap in Hebrew optics and lens anatomy. The existing Mishnaic Hebrew word קָמוּר (kamur), appearing in the Mishnah (Ohalot 3:7), had long denoted a dome or arch shape, but could refer to either a shape that bulges outward or one that curves inward — an ambiguity that was untenable in precise medical and optical contexts.
To create a matching antonym, Feigenbaum derived קָעוּר from the root ק-ע-ר, the same root underlying the common noun קְעָרָה (ke'ara, "bowl" or "dish"). The semantic logic is elegant: a bowl is the archetypal concave form, something that curves inward. By applying the same adjectival pattern as קָמוּר, he produced a parallel pair: קָמוּר for convex (outward-curving) and קָעוּר for concave (inward-curving).
Feigenbaum was a remarkable figure in the revival of Hebrew. Born in 1885, he immigrated to Palestine at age 28 in 1913, settling in Jerusalem's Old City on the same street as Eliezer Ben-Yehuda and David Yellin. As one of the first ophthalmologists in the country, he fought the trachoma epidemic blinding hundreds, while simultaneously working to establish Hebrew as the language of medicine. After spending World War I in exile in Damascus, he returned to lead the ophthalmology department at Hadassah Hospital and helped train the first cohort of Hebrew-speaking nurses. It was this educational work that prompted his extraordinary burst of lexical creativity.
The glossary at the back of his 1927 textbook, where Feigenbaum marked his own coinages with an asterisk, contained approximately 40 new terms that have been absorbed into everyday Hebrew. קָעוּר was one of them. The pair קָמוּר/קָעוּר is now standard in Hebrew, appearing in mathematics, optics, physics, and everyday speech.
Key Quotes
"חִדשתי גם אני מונחים, אבל רק כשעלה בידי למצוא בטוי מתאים מכל בחינה בשביל מושג זה או אחר, ובאין-ברירה השתמשתי גם במלה לועזית" — Aryeh Feigenbaum, introduction to Ha'Ayin, 1927
Timeline
- Mishnaic era: קָמוּר attested in Mishnah Ohalot 3:7 with undifferentiated meaning of "arch-shaped"
- 1913: Feigenbaum immigrates to Palestine, joins the Hebrew language movement
- 1927: Feigenbaum publishes his nursing textbook and coins קָעוּר (along with ~40 other terms)
- 20th century: The pair קָמוּר/קָעוּר established as the standard Hebrew terms for convex/concave
Related Words
- קָמוּר — convex (Mishnaic; the existing antonym Feigenbaum's coinage was paired with)
- קְעָרָה — bowl, dish (the source noun from which קָעוּר was derived)
- קַרְנִית — cornea (another Feigenbaum coinage from the same 1927 textbook)
- רִשְׁתִּית — retina (another Feigenbaum coinage from 1927)
- עֲקֻמָּה — curve/graph (another Feigenbaum coinage)