zenith line, n.

zenith-line
http://www.oed.com/dictionary/zenith-line_n%3Ftab%3Dmeaning_and_use
Revised 2018

# zenith linenoun

## Factsheet

### What does the noun zenith line mean?

There are two meanings listed in OED's entry for the noun zenith line. See ‘Meaning & use’ for definitions, usage, and quotation evidence.

### How common is the noun zenith line?

Fewer than 0.01occurrences per million words in modern written English

1790 | 0.0014
1800 | 0.0011
1810 | 0.0011
1820 | 0.0012
1830 | 0.0006
1840 | 0.0007
1850 | 0.0008
1860 | 0.0007
1870 | 0.0021
1880 | 0.0019
1890 | 0.0017
1900 | 0.0017
1910 | 0.0017
1920 | 0.0019
1930 | 0.0018
1940 | 0.0005
1950 | 0.0005
1960 | 0.0005
1970 | 0.0005
1980 | 0.0005
1990 | 0.0003
2000 | 0.0003
2010 | 0.0003

### Where does the noun zenith line come from?

Earliest known use

late 1500s

The earliest known use of the noun zenith line is in the late 1500s.

OED's earliest evidence for zenith line is from 1585, in the writing of John Blagrave, mathematician.

### Nearby entries

1. Zener, n.² 1949–
2. Zengakuren, n. 1950–
3. Zen garden, n. 1937–
4. zenick, n. 1801–1900
5. zenitfer, n. 1596–
6. zenith, n. & adj. a1387–
7. zenithal, adj.?1731–
8. zenithal projection, n. 1877–
9. zenith-borne, adj. 1865–86
10. zenith distance, n. 1588–
11. zenith line, n.1585–
12. zenith point, n. 1585–
13. zenith sector, n. 1775–
14. zenith sweep, n. 1790–
15. zenith telescope, n. 1803–
16. zenith tube, n. 1825–
17. zenithward, n., adv., & adj. 1655–
18. zenithwards, adv. 1826–
19. Zenker, n.¹ 1872–
20. Zenker, n.² 1894–
21. Zen-like, adj. a1908–

## Meaning & use

Now rare.

1. 1585–
   a. An arc from the zenith to the horizon, which it intersects at right angles (= azimuth n. 1), esp. to the point due east on the horizon; b. a straight vertical line between the zenith point at a given location and the centre of the earth.
   1. 1585

      > The 15. azimuth reckoned from the East or zenith line.

      J. Blagrave, Math. Iewel 39
   2. a1652

      > How to draw and divide the Ellipsis upon any Plain, to an Index that stands upright..to the Zenith line of the place, or perpendicular to the plain of the Horizon.

      S. Foster, Elliptical Horologiography (1654) 69 (heading)
   3. 1778

      > The imaginary Lines then, perpendicular to the Zenith Line from the different Elevations..are to be understood as the respective true Horizons.

      N. D. Falck, Ready Observator (ed. 2) 80
   4. 1871

      > The white streamers [of the aurora] extended almost to the eastern horizon, and some were to the south of the zenith line.

      Exchange & Mart 19 April 480/1
   5. 1987

      > Your latitude is the angle formed at the Earth's centre between the equator and your zenith-line.

      J. Raban in Granta No. 10. 29
   astronomy
   1. azimuth c1400–
      An arc of the heavens extending from the zenith to the horizon which it cuts at right angles; the quadrant of a great circle of the sphere…
   2. vertical circle 1559–
      Of or pertaining to, placed or situated at, passing through, the vertex or zenith; occupying a position… An azimuth-circle (see azimuth, n. 1).
   3. zenith line 1585–
      a. An arc from the zenith to the horizon, which it intersects at right angles (= azimuth, n. 1), esp. to the point due east on the horizon; b. a…
   4. vertical 1669–
      A vertical circle, line, or plane.
   View in Historical Thesaurus

## Frequency

zenith line typically occurs fewer than 0.01 times per million words in modern written English.

zenith line is in frequency band 1, which contains words occurring fewer than 0.001 times per million words in modern written English. More about OED's frequency bands

Frequency data is computed programmatically, and should be regarded as an estimate.

### Frequency of zenith line, n., 1790–2010

* Occurrences per million words in written English

Historical frequency series are derived from Google Books Ngrams (version 2), a data set based on the Google Books corpus of several million books printed in English between 1500 and 2010.

The overall frequency for a given word is calculated by summing frequencies for the main form of the word, any plural or inflected forms, and any major spelling variations.

For sets of homographs (distinct entries that share the same word-form, e.g. mole, n.¹, mole, n.², mole, n.³, etc.), we have estimated the frequency of each homograph entry as a fraction of the total Ngrams frequency for the word-form. This may result in inaccuracies.

Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the Google Books corpus.

Decade | Frequency per million words
--- | ---
1790 | 0.0014
1800 | 0.0011
1810 | 0.0011
1820 | 0.0012
1830 | 0.0006
1840 | 0.0007
1850 | 0.0008
1860 | 0.0007
1870 | 0.0021
1880 | 0.0019
1890 | 0.0017
1900 | 0.0017
1910 | 0.0017
1920 | 0.0019
1930 | 0.0018
1940 | 0.0005
1950 | 0.0005
1960 | 0.0005
1970 | 0.0005
1980 | 0.0005
1990 | 0.0003
2000 | 0.0003
2010 | 0.0003

Originally published as part of the entry for zenith, n. & adj.

zenith, n. & adj. was revised in June 2018.