Apophony

In linguistics, apophony is an alternation of vowel within a word that indicates grammatical information. It is also known as ablaut, gradation, mutation, alternation, internal modification, stem modification, stem alternation, replacive morphology, stem mutation, or internal inflection.

Description

Apophony is exemplified in English as the internal vowel alternations that produce such related words as

sng, sng, sng, sng
bnd, bnd
bld, bld, bld
brd, brd, brd
dm, dm
fd, fdder, fd, fd
l, l
rse, rse, rsen
wve, wft, wve
ft, ft
gse, gsling, gse
tth, tth

The difference in these vowels marks variously a difference in tense or aspect, transitivity, part of speech, or grammatical number.
That these sound alternations function grammatically can be seen as they are often equivalent to grammatical suffixes. Compare the following:

Present tense	Past tense
jump	jump
sng	sng
Singular	Plural
book	book
gse	gse

The vowel alternation between i and a indicates a difference between present and past tense in the pair sing/sang. Here the past tense is indicated by the vowel a just as the past tense is indicated on the verb jump with the past tense suffix -ed. Likewise, the plural suffix -s on the word books has the same grammatical function as the presence of the vowel ee in the word geese.
Consonants, too, can alternate in ways that are used grammatically. An example is the pattern in English of verb-noun pairs with related meanings but differing in voicing of a postvocalic consonant:

Verb voiced	Noun unvoiced
advie	advie
beliee	belie
breae	brea
gie	git
houe	houe
lie	lie
rie	rit
ue	ue
weae	wet
wreae	wrea

Most instances of apophony develop historically from changes due to phonological assimilation that are later grammaticalized when the environment causing the assimilation is lost. Such is the case with English goose/geese and breath/breathe.

Types

Apophony may involve various types of alternations, including vowels, consonants, prosodic elements, and even smaller features, such as nasality.
The sound alternations may be used inflectionally or derivationally. The particular function of a given alternation will depend on the language.

Vowel gradation

Apophony often involves vowels. Indo-European ablaut and Germanic umlaut, mentioned above, are well attested examples. Another example is from Dinka:

Singular	Plural	Gloss	Vowel alternation
		'field/fields'
		'frame/frames'

The vowel alternation may involve more than just a change in vowel quality. In Athabaskan languages, such as Navajo, verbs have series of stems where the vowel alternates indicating a different tense-aspect. Navajo vowel ablaut, depending on the verb, may be a change in vowel, vowel length, nasality, and/or tone. For example, the verb stem 'to handle an open container' has a total of 16 combinations of the 5 modes and 4 aspects, resulting in 7 different verb stem forms.

	Imperfective	Perfective	Progressive- future	Usitative- iterative	Optative
Momentaneous
Continuative
Distributive
Conative		-	-	-	-

Another verb stem | 'to cut' has a different set of alternations and mode-aspect combinations, resulting in 3 different forms :

	Imperfective	Perfective	Progressive- future	Usitative- iterative	Optative
Momentaneous
Continuative
Semelfactive

Prosodic apophony

Various prosodic elements, such as tone, syllable length, and stress, may be found in alternations. For example, Vietnamese has the following tone alternations which are used derivationally:
Albanian uses different vowel lengths to indicate number and grammatical gender on nouns:

"stone"	"stones"
"two "	"two "

English has [Initial-stress-derived noun|alternating stress patterns] that indicate whether related words are nouns or verbs. This tends to be the case with words in English that came from Latin:

noun	verb
cóntrast	contrást
cónvict	convíct
ínsult	insúlt
óbject	objéct
pérmit	permít
pérvert	pervért
récord	recórd
súbject	subjéct

Prosodic alternations are sometimes analyzed as not as a type of apophony but rather as prosodic affixes, which are known, variously, as suprafixes, superfixes, or simulfixes.

Consonant apophony

Consonant alternation is commonly known as consonant mutation or consonant gradation. Bemba indicates causative verbs through alternation of the stem-final consonant. Here the alternation involves spirantization and palatalization:

Intransitive verb	Causative verb
italic=unset 'to be lost'	italic=unset 'to cause to be lost'
italic=unset 'to be deaf'	italic=unset 'to cause to be deaf'
italic=unset 'to fall'	italic=unset 'to cause to fall'
italic=unset 'to walk'	italic=unset 'to cause to walk'
italic=unset 'to hunt'	italic=unset 'to cause to hunt'
italic=unset 'to grow'	italic=unset 'to cause to grow'

Celtic languages are well known for their initial consonant mutations.

Indo-European linguistics

Indo-European ablaut

In Indo-European linguistics, ablaut is the vowel alternation that produces such related words as sing, sang, sung, and song. The difference in the vowels results from the alternation of the vowel e with the vowel o or with no vowel.
To cite a few other examples of Indo-European ablaut, English has a certain class of verbs, called strong verbs, in which the vowel changes to indicate a different grammatical tense-aspect.

Imperative	Preterite	Past participle	Vowel alternation
swm	swm	swm	phonetically:
fll	fll	fllen	phonetically:
drve	drve	drven	phonetically:

As the examples above show, a change in the vowel of the verb stem creates a different verb form. Some of the verbs also have a suffix in the past participle form.

Umlaut

In Indo-European linguistics, umlaut is the vowel fronting that produces such related words as foot > feet or strong > strength. The difference in the vowels results from the influence of an, or at the end of the word causing the stem vowel to be pulled forward. Some weak verbs show umlaut in the present tense, with the past tense representing the original vowel: bought > buy. Hundreds of similar examples can be found in English, German, Dutch and other languages.
Germanic a-mutation is a process analogous to umlaut, but involving the influence of a low vowel such as causing a high vowel in the stem to lower.

Ablaut versus umlaut

In Indo-European historical linguistics the terms ablaut and umlaut refer to different phenomena and are not interchangeable. Ablaut is a process that dates back to Proto-Indo-European times, occurs in all Indo-European languages, and refers to unpredictable vowel alternations of a specific nature. From an Indo-European perspective, it typically appears as a variation between o, e, and no vowel, although various sound changes result in different vowel alternations appearing in different daughter languages. Umlaut, meanwhile, is a process that is particular to the Germanic languages and refers to a variation between back vowels and front vowels that was originally phonologically predictable, and was caused by the presence of an or in the syllable following the modified vowel.
From a diachronic perspective, the distinction between ablaut and umlaut is very important, particularly in the Germanic languages, as it indicates where and how a specific vowel alternation originates. It is also important when taking a synchronic perspective on old Germanic languages such as Old English, as umlaut was still a very regular and productive process at the time. When taking a synchronic perspective on modern languages, however, both processes appear very similar. For example, the alternations seen in sing/sang/sung and foot/feet both appear to be morphologically conditioned and phonologically unpredictable.
By analogy, descriptive linguists discussing synchronic grammars sometimes employ the terms ablaut and umlaut, using ablaut to refer to morphological vowel alternation generally and umlaut to refer to any type of regressive vowel harmony. Ambiguity can be avoided by using alternative terms for the broader sense of the words.

Stem alternations and other morphological processes

Stem modifications may co-occur with other morphological processes, such as affixation. An example of this is in the formation of plural nouns in German:

Singular	Plural
italic=unset 'book'	italic=unset 'books'
italic=unset 'house'	italic=unset 'houses'

Here the singular/plural distinction is indicated through umlaut and additionally by a suffix -er in the plural form. English also displays similar forms with a -ren suffix in the plural and a -en suffix in the past participle forms along with the internal vowel alternation:

child	children
drive	driv'en'

Chechen features this as well:

Singular	Plural
italic=unset 'mountain'	italic=unset 'mountains'
italic=unset 'language'	italic=unset 'languages'

A more complicated example comes from Chickasaw where the positive/negative distinction in verbs displays vowel ablaut along with prefixation and infixation :

Positive	Negative
'I'm dancing'	'I'm not dancing'

Transfixation

The nonconcatenative morphology of the Afroasiatic languages is sometimes described in terms of apophony. The alternation patterns in many of these languages is quite extensive involving vowels and consonant gemination. The alternations below are of Modern Standard Arabic, based on the root 'write' :

Word	Gloss	Alternation pattern
	'he wrote'
	'it was written'
	'he writes'
	'it is written'
	'writing ; writer'
	'writers'
	'written'
	' writing'
	'book'
	'books'
	'he corresponded with'
	'he caused to write'
	'he was caused to write'

Other analyses of these languages consider the patterns not to be sound alternations, but rather discontinuous roots with discontinuous affixes, known as transfixes. Some theoretical perspectives call up the notion of morphological templates or morpheme "skeletons".
It would also be possible to analyze English in this way as well, where the alternation of goose/geese could be explained as a basic discontinuous root g-se that is filled out with an infix -oo- "" or -ee- "". Many would consider this type of analysis for English to be less desirable as this type of infixal morphology is not very prevalent throughout English and the morphemes -oo- and -ee- would be exceedingly rare.

Replacive morphemes

Another analytical perspective on sound alternations treats the phenomena not as merely alternation but rather a "replacive" morpheme that replaces part of a word. In this analysis, the alternation between goose/geese may be thought of as goose being the basic form where -ee- is a replacive morpheme that is substituted for oo.
This usage of the term morpheme, however, is more in keeping with Item-and-Process models of morphology instead of Item-and-Arrangement models.

Ablaut-motivated compounding

Ablaut reduplication, or ablaut-motivated compounding, is a type of word formation of "expressives", in which words are formed by reduplication of a base and alternation of the internal vowel.
The pattern of vowel alternation in English follows a front to back vowel order, which among clipped vowels means a subset of, as in:

bing-bang-boom
bish-bash-bosh
criss-cross
shilly-shally
snip-snap
splish-splash
tic-tac-toe
tick-tock
ticky-tacky
wishy-washy
zig-zag

And partially in eeny, meeny, miny, moe.
In many Turkic languages the vowel pattern is low to high, as in Turkish and .
Examples from Japanese include:

'rattle'
'rustle'

Examples from Chinese include:

叽里咕噜
噼里啪啦

Some languages do not appear to have a preferred order, for example Mongolian with both pay-puy and puy-pay.