zero day, n.

zero-day
http://www.oed.com/dictionary/zero-day_n%3Ftab%3Dmeaning_and_use
Revised 2018

# zero daynoun

## Factsheet

### What does the noun zero day mean?

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

zero day has developed meanings and uses in subjects including

military (1910s) computing (1990s)

### How common is the noun zero day?

About 0.02occurrences per million words in modern written English

1910 | 0.023
1920 | 0.024
1930 | 0.024
1940 | 0.023
1950 | 0.023
1960 | 0.021
1970 | 0.021
1980 | 0.02
1990 | 0.019
2000 | 0.018
2010 | 0.018

### How is the noun zero day pronounced?

#### British English

/ˈzɪərəʊ deɪ/
ZEER-oh day

#### U.S. English

/ˈzɪroʊ ˌdeɪ/
ZEER-oh day
/ˈziroʊ ˌdeɪ/
ZEER-oh day

### Where does the noun zero day come from?

Earliest known use

1910s

The earliest known use of the noun zero day is in the 1910s.

OED's earliest evidence for zero day is from 1917, in Attack Brit. 9th Corps Messines Ridge.

zero day is formed within English, by compounding.

Etymons: zero n., day n.

### Nearby entries

1. zero, v. 1813–
2. zeroable, adj. 1956–
3. zero balance, adj. 1974–
4. zero-base, adj. 1962–
5. zero-based, adj. 1963–
6. zero beat, n. 1920–
7. zero-carbon, adj. 1990–
8. zero-coupon, adj. 1979–
9. zero creep, n. 1904–
10. zero crossing, n. 1941–
11. zero day, n.1917–
12. zero-defect, adj. 1964–
13. zero derivation, n. 1960–
14. zero derivative, adj. & n. 1948–
15. zero-derived, adj. 1971–
16. zero-dimensional, adj. 1880–
17. zero-emission, n. & adj. 1952–
18. zero-energy, adj. 1947–
19. zero-field, adj. 1915–
20. zero-G, adj. & n. 1950–
21. zero grade, n. 1888–

## Etymology

### Summary

Formed within English, by compounding.
Etymons: zero n., day n.
< zero n. + day n.

With sense 1 compare slightly earlier zero hour n.

## Meaning & use

1. 1.
   1917–
   Military. The day on which a military operation is scheduled to begin. Also in extended use: the day on which any significant event or activity is scheduled to begin or take place. Cf. zero hour n. 1.
   1. 1917

      > The assault, which will be preceded by a five days' artillery bombardment, will take place about dawn on Zero day.

      Attack Brit. 9th Corps Messines Ridge (U.S. War Dept. Doc. No. 653) 12
   2. 1947

      > I..fixed a zero-day three months ahead.

      L. Hastings, Dragons are Extra iv. 80
   3. 1952

      > Stilfontein's zero day is Tuesday next, when the mine will officially be producing gold.

      Financial Times 30 June 3/2
   4. 1978

      > 20th October had been fixed as Zero Day for rocket attacks on London to begin.

      R. V. Jones, Most Secret War xxxix. 350
   5. 2007

      > Working parties had filled in shell craters and bridged trenches in order to have roads built as far as the front line by zero day.

      P. D. Dickson, Thoroughly Canadian General iii. 53
   military
   1. zero 1849–
      The initial point of a process or sequence of events; the starting point, the absolute beginning; (Military) the time or day when an attack or…
   2. zero day 1917–
      Military. The day on which a military operation is scheduled to begin. Also in extended use: the day on which any significant event or activity is…
   3. Z-day 1925–
      = zero day, n. 1.
   View in Historical Thesaurus
   1. release date 1904–
      The date on which something is released; (now esp.) a date fixed in advance for the release (release, n. II.8) of a film, recording, or similar…
   2. effective date 1909–
      The date on which an order, ruling, appointment, etc., takes effect.
   3. zero hour 1915–
      The time at which a military operation is scheduled to begin. Also in extended use: the time at which any (typically significant) event is…
   4. zero day 1917–
      Military. The day on which a military operation is scheduled to begin. Also in extended use: the day on which any significant event or activity is…
   5. start date 1920–
      The date on which something (esp. a job) commences or begins; starting date.
   6. countdown 1953–
      The action of counting in reverse, from a given number to zero, usually in seconds, to mark the lapse of time before an explosion, the launching of…
   7. T 1959–
      Used as a symbol. Astronautics. T represents the time at which a spacecraft is due to be launched.
   View in Historical Thesaurus
   1. opening day 1798–
      The first day of an event or season; the first day of operation or business.
   2. magazine-day 1821–
      The day on which a particular magazine is issued to the trade.
   3. first 1868–
      In dates: the first day of a month. Without modifier. spec.: (in the language of sportspeople) the first day of a particular month, when the season…
   4. zero day 1917–
      Military. The day on which a military operation is scheduled to begin. Also in extended use: the day on which any significant event or activity is…
   View in Historical Thesaurus
2. 2.
   Computing.
   1. 2.a.
      1993–
      attributive. Designating (an item of) commercial software, media, etc., illegally made available via the internet on the same day as (or sometimes earlier than) its official release. Chiefly in zero day warez (see warez n.).
      1. [1992

         > The target for all these groups was ‘zero wares’, software that had been cracked less than 24 hours earlier—zero days.

         Sydney Morning Herald (Nexis) 28 September 18]
      2. 1993

         > There was talk in this group about zero day warez.

         Goal! Piracy in comp.sys.amiga.advocacy 28 June (Usenet newsgroup, accessed 11 Jan. 2018)
      3. 2004

         > Zero Day cracks appear even before the products have been released.

         What Crap is This? in comp.os.linux.advocacy (Usenet newsgroup, accessed 11 Jan. 2018) 24 July
      4. 2017

         > Oh that kind of pirate. I was going to bring up BitTorrent and zero day warez.

         @MCWronski 19 September in twitter.com (accessed 11 Jan. 2018)
      computing
   2. 2.b.
      2000–
      attributive. Designating a software vulnerability that is unknown to the developer or vendor, making it vulnerable to an attack until it is discovered and fixed; designating an attack or method of attack which exploits such a vulnerability.
      1. 2000

         > The so-called zero day exploit list..features a minimum of 100 fresh vulnerabilities a week.

         ‘We're the Good Guys’ claim Hackers in alt.hit2000.nl 14 April (Usenet newsgroup, accessed 11 Jan. 2018)
      2. 2006

         > The attacks..use phishing e-mails to get employees to open e-mail attachments or visit Web sites that download Trojans targeting ‘zero-day’ vulnerabilities in common apps.

         InfoWorld 30 October 26/1
      3. 2017

         > The breach could be the result of a so-called zero-day attack, one that exploits a flaw in software not identified or patched by the supplier.

         Times (Nexis) 16 June 16
      computing

## Pronunciation

### British English

/ˈzɪərəʊ deɪ/
ZEER-oh day

### U.S. English

/ˈzɪroʊ ˌdeɪ/
ZEER-oh day
/ˈziroʊ ˌdeɪ/
ZEER-oh day

####

##### Consonants

- ppea
- ttea
- kkey
- bbuy
- ddye
- ɡguy
- tʃchore
- dʒjay
- ffore
- θthaw
- ssore
- ʃshore
- vvee
- ðthee
- zzee
- ʒbeige
- xloch
- hhay
- llay
- ɬrhingyll
- rray
- wway
- jyore
- mmay
- nnay
- ŋsing

Some consonants can take the function of the vowel in unstressed syllables. Where necessary, a syllabic marker diacritic is used, hence /ˈpɛtl/ but /ˈpɛtl̩i/.

##### Vowels

- iːfleece
- ihappy
- ɪkit
- ɛdress
- atrap, bath
- ɑːstart, palm, bath
- ɒlot
- ɔːthought, force
- ʌstrut
- ʊfoot
- uːgoose
- əletter
- əːnurse
- ɪənear
- ɛːsquare
- ʊəcure
- eɪface
- ʌɪpride
- aʊmouth
- əʊgoat
- ɔɪvoice
- ãgratin
- ɒ̃salon
- ᵻ(/ɪ/-/ə/)
- ᵿ(/ʊ/-/ə/)

##### Other symbols

- The symbol ˈ at the beginning of a syllable indicates that that syllable is pronounced with primary stress.
- The symbol ˌ at the beginning of a syllable indicates that that syllable is pronounced with secondary stress.
- Round brackets ( ) in a transcription indicate that the symbol within the brackets is optional.

View the pronunciation model here.

####

##### Consonants

- ppea
- ttea
- kkey
- bbuy
- ddye*
- ɡguy
- tʃchore
- dʒjay
- ffore
- θthaw
- ssore
- ʃshore
- vvee
- ðthee
- zzee
- ʒbeige
- xloch
- hhay
- llay
- rray
- wway
- jyore
- mmay
- nnay
- ŋsing

* /d/ also represents a 'tapped' /t/ as in

Some consonants can take the function of the vowel in unstressed syllables. Where necessary, a syllabic marker diacritic is used, hence /ˈpɛd(ə)l/ but /ˈpɛdl̩i/.

##### Vowels

- ifleece, happy
- ɪkit
- ɛdress
- ætrap, bath
- ɑlot, palm, cloth, thought
- ɑrstart
- ɔcloth, thought
- ɔrnorth, force
- ʊfoot
- ugoose
- əstrut, comma
- ərnurse, letter
- ɪ(ə)rnear
- ɛ(ə)rsquare
- ʊ(ə)rcure
- eɪface
- aɪpride
- aʊmouth
- oʊgoat
- ɔɪvoice
- ɑ̃gratin
- æ̃salon
- ᵻ(/ɪ/-/ə/)
- ᵿ(/ʊ/-/ə/)

##### Other symbols

- The symbol ˈ at the beginning of a syllable indicates that that syllable is pronounced with primary stress.
- The symbol ˌ at the beginning of a syllable indicates that that syllable is pronounced with secondary stress.
- Round brackets ( ) in a transcription indicate that the symbol within the brackets is optional.

View the pronunciation model here.

####

Simple text respell breaks words into syllables, separated by a hyphen. The syllable which carries the primary stress is written in capital letters. This key covers both British and U.S. English Simple Text Respell.

##### Consonants

b, d, f, h, k, l, m, n, p, r, s, t, v, w and z have their standard English values

- gguy
- jjay
- yyore
- chchore
- khloch
- shshore
- ththaw
- dhthee
- zhbeige

##### Vowels

- atrap
- ahpalm
- airsquare
- arstart
- arrcarry (British only)
- awthought
- ayface
- a(ng)gratin
- edress
- eefleece
- eerdeer
- errmerry
- ikit
- ighpride
- irrmirror
- olot (British only)
- ohgoat
- oogoose
- oorcure
- orforce
- orrsorry (British only)
- owmouth
- oyvoice
- o(ng)salon
- ustrut
- uhletter
- urnurse
- urrhurry
- uufoot

## Forms

### Variant forms

Also (in sense 1) with capital initials.

## Frequency

zero day typically occurs about 0.02 times per million words in modern written English.

zero day is in frequency band 3, which contains words occurring between 0.01 and 0.1 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 zero day, n., 1910–2010

* 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
--- | ---
1910 | 0.023
1920 | 0.024
1930 | 0.024
1940 | 0.023
1950 | 0.023
1960 | 0.021
1970 | 0.021
1980 | 0.02
1990 | 0.019
2000 | 0.018
2010 | 0.018

### Frequency of zero day, n., 2017–2024

* Occurrences per million words in written English

Modern frequency series are derived from a corpus of 20 billion words, covering the period from 2017 to the present. The corpus is mainly compiled from online news sources, and covers all major varieties of World English.

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 corpus.

Period | Frequency per million words
--- | ---
2017 | 0.33
2018 | 0.36
2019 | 0.45
2020 | 0.53
2021 | 0.58
2022 | 0.58
2023 | 0.62
2024 | 0.55

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

zero day, n. was revised in June 2018.

zero day, n. was last modified in December 2023.