<Germanzwitter-ion (F. W. Küster 1897, in Zeitschr. f. anorg. Chem. XIII. 136), <zwitter hermaphrodite, hybrid (Old High Germanzwitar(a)n, <zwi-twi-comb. form) + ionionn.
Meaning & use
Chemistry.
1906–
A molecule or ion having separate positively and negatively charged atoms or groups.
1906
Ions which are simultaneously electro-positive and electro-negative (Bredig), and which Küster calls ‘Zwitter-ions’, i.e. hermaphrodite-ions. Thus the ‘Zwitter-ion’ of glycocoll is the group H3N—CH2—COO.
G. Mann, Chemistry of Proteids vi. 210
1925
The ‘isomeric change’ now takes the form of a fission of the molecule by the rupture of a bond, the final ionisation of which provides the electric charges which are needed to neutralise those already present in the ‘Zwitterion’.
Journal of Chemical Societyvol. 127 1381
1937
One of the greatest advances in the understanding of the physico~chemical behaviour of amino-acids and proteins is due to the zwitterion theory introduced by Bjerrum in 1923.
Nature 18 September 492/1
1948
The products of [penicillin] inactivation are zwitter-ions.
Endeavourvol. 7 85/2
1949
The penicilloic acids are zwitterions with two acid groups and one basic group.
E. Chain in H. W. Florey et al., Antibioticsvol. II. xxii. 847
1968
At the pH of living cells, lecithin forms a balanced zwitterion.
D. W. Wood, Principles of Animal Physiology iii. 35
1982
It is useful to calculate the exact pH at which an amino acid is electrically neutral and in its zwitterion form.
R. M. Schultz in T. M. Devlin, Textbook of Biochemistry ii. 41
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.
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.
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
Formerly also zwitter-ion and with capital initial.
Frequency
zwitterion typically occurs about 0.06 times per million words in modern written English.
zwitterion 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 zwitterion, n., 1920–2010
* 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
1920
0.037
1930
0.044
1940
0.049
1950
0.052
1960
0.061
1970
0.06
1980
0.061
1990
0.061
2000
0.059
2010
0.055
Frequency of zwitterion, 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.