transition regionn.
/tranˈzɪʃn ˌriːdʒ(ə)n/, /trɑːnˈzɪʃn ˌriːdʒ(ə)n/, /tranˈsɪʃn ˌriːdʒ(ə)n/, /trɑːnˈsɪʃn ˌriːdʒ(ə)n/, /tranˈsɪʒn ˌriːdʒ(ə)n/, /trɑːnˈsɪʒn ˌriːdʒ(ə)n/, U.S. /trænˈzɪʃ(ə)n ˌridʒ(ə)n/ 1. A region where the characteristics of one adjacent section or division give way to those of another, sometimes exhibiting features of both.
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1815 Med. Repository New Ser. 2 94 The act of June 1, incorporating a company for the purpose of digging and manufacturing Lead ore, in the county of Ulster, has opened the way for valuable disclosures in the transition region where their mine lies.
1876 A. Woeikof Winds of Globe in Smithsonian Contrib. Knowl. 20 693 E. Missouri and N. E. Arkansas are also transition regions between the countries east and west of the Mississippi.
1936 Sewage Wks Jrnl. 8 745 Grit in sewage plants settles almost wholly in the transition region.
2017 Independent (Nexis) 18 May (Environment section) Species in the forest-prairie transition region moved west at 30km per decade.
2. spec.
a. Botany. The region in a plant axis where the structures of the root meet those of the shoot or stem.
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1899 Trans. Amer. Microsc. Soc. 1898 20 114 The structure of the root, and the structure, location and extent of the transition-region present no appreciable difference from the structure of the same organs in Allionia hirsuta.
1960 K. Esau Anat. Seed Plants iii. 27 The change in character of the histologic pattern in the successive levels of the transition region is gradual.
2015 Plant Physiol. 169 2296/1 Completion of germination is the result of cell expansion and not cell division within the hypocotyl-radicle transition region.
b. Astronomy. The thin layer of the sun's atmosphere between the chromosphere and the corona, produced by heat flowing from the latter into the former.
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1939 Pop. Astron. 47 16 The transition region is also effective in producing the absorption line.
1972 New Scientist 6 July 29/2 The transition region is the source of many small jets known as spicules.
2008 K. Saha Earth's Atmosphere vii. 96 Ultraviolet radiation also comes out of the chromosphere and the transition region.
c. Electronics.
(a) The region between the passband and stopband in the frequency response of a filter (filter n. 4d).
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1942 U.S. Patent 2,270,416 1/1 It is further desirable that the transition region from pass to stop should occupy the narrowest possible band of frequencies within the pass range.
1989 P. Horowitz & W. Hill Art of Electronics (ed. 2) v. 269/2 The Butterworth filter produces the flattest passband response, at the expense of steepness in the transition region from passband to stopband.
2005 B. Baker Baker's Dozen iv. 96 (caption) If you increase the number of poles in a Butterworth low-pass filter design, you get a sharper roll-off through the transition region.
(b) Electronics. In a semiconductor device: the junction between an N-type and P-type semiconductor.
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1949 Bell Syst. Techn. Jrnl. 28 436 Appreciable hole currents may flow into the n-region beyond the transition region.
1969 J. J. Sparkes Transistor Switching i. 15 This results in a narrowing of the collector transition region and a widening of the base region.
2009 J. Sóylom Fund. of Physics of Solids II. xxvii. 546 Two oppositely directed currents flow in the transition region.
This entry has been updated (OED Third Edition, March 2019; most recently modified version published online March 2022).
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