{{Short description|Smallest meaningful unit in a language}}
{{Distinguish|morphine|morpheein}}
{{Unreferenced section|date=September 2011}}
{{Linguistics}}
A '''morpheme''' is the smallest meaningful constituent of a linguistic expression, especially within a word.<ref>{{Cite book |last=Haspelmath |first=Martin |title=Understanding Morphology |date=2010 |publisher=Hodder Education |others=Andrea D. Sims |isbn=978-0-340-95001-2 |edition=2nd |location=London |page=14 |language=en |oclc=671004133}}</ref> Many words are themselves standalone morphemes, while other words contain multiple morphemes; in linguistic terminology, this is the distinction, respectively, between [[bound and free morphemes|free and bound morphemes]]. The field of [[linguistics|linguistic]] study dedicated to morphemes is called [[morphology (linguistics)|morphology]].<ref>{{Cite journal |last=Lahrouchi |first=Mohamed |date=31 Oct 2023 |title=morphology |url=https://hal.science/hal-04266255v1/file/Morphology-Classes1-2-3-Lahrouchi_Ilia%20State%20University%20Tbilisi2023.pdf |journal=hal.science}}</ref>

In English, inside a word with multiple morphemes, the main morpheme that gives the word its basic meaning is called a [[root (linguistics)|root]] (such as ''cat'' inside the word ''cats''), which can be bound or free. Meanwhile, additional bound morphemes, called [[affix]]es, may be added before or after the root, like the ''-s'' in ''cats'', which indicates plurality but is always bound to a root [[noun]] and is not regarded as a word on its own.<ref>{{cite web|last=Kemmer|first=Suzanne|title=Structure|website=Words in English|url=http://www.ruf.rice.edu/~kemmer/Words04/structure/index.html|access-date=10 April 2014|archive-date=31 August 2004|archive-url=https://web.archive.org/web/20040831200411/http://www.ruf.rice.edu/~kemmer/Words04/structure/index.html|url-status=live}}</ref> However, in some languages, including English and [[Latin]], even many roots cannot stand alone; i.e., they are bound morphemes. For instance, the Latin root ''reg-'' ('king') must always be suffixed with a case marker: ''regis'', ''regi'', ''rex'' (''reg+s''), etc. The same is true of the English root ''nat(e)'' &mdash; ultimately inherited from a Latin root meaning "birth, born" &mdash; which appears in words like ''native'', ''nation'', ''nature'', ''innate'', and ''[[neonate]]''. 

These sample English words have the following morphological analyses:
* "Unbreakable" is composed of three morphemes: ''un-'' (a bound morpheme signifying [[Affirmation and negation|negation]]), ''break'' (a verb that is the root of ''unbreakable'': a free morpheme), and ''-able'' (a bound morpheme as an adjective suffix signifying "capable of, fit for, or worthy of").<ref>{{Cite Merriam-Webster|able}}</ref>
* The plural morpheme for regular nouns (''-s'') has three [[allomorph]]s: it is pronounced {{IPA|/s/}} (e.g., in ''cats'' {{IPAc-en|k|æ|t|s}}), {{IPA|/ɪz/}} or {{IPA|/əz/}} (e.g., in ''dishes'' {{IPAc-en|d|ɪ|ʃ|ᵻ|z}}), and {{IPA|/z/}} (e.g., in ''dogs'' {{IPAc-en|d|ɒ|ɡ|z}}), depending on the pronunciation of the root.

== Classification ==
===Free and bound morphemes===
{{main|Bound and free morphemes}}
Every morpheme can be classified as free or bound:<ref>{{cite web |url=http://ling.ohio-state.edu/~kdk/201/autumn01/slides/morphology-4up.pdf |title=Morphology |archive-url=https://web.archive.org/web/20140320115048/http://www.ling.ohio-state.edu//~kdk/201/autumn01/slides/morphology-4up.pdf |archive-date=2014-03-20 |access-date=19 March 2014 |work=Linguistics 201: Introduction to Language in the Humanities |date=October 22, 2001 |first1=Kordula |last1=De Kuthy }}</ref>
* Free morphemes can function independently as words (e.g. ''town'', ''dog'') and can appear within [[lexeme]]s (e.g. ''town hall'', ''doghouse'').
* Bound morphemes appear only as parts of words, always in conjunction with a [[root (linguistics)|root]] and sometimes with other bound morphemes. For example, ''un-'' appears only when accompanied by other morphemes to form a word. Most bound morphemes in English are affixes, specifically [[prefixes]] and [[suffixes]]. Examples of suffixes are ''-tion'', ''-sion'', ''-tive'', ''-ation'', ''-ible'', and ''-ing''. Bound morphemes that are not affixed are called [[cranberry morpheme]]s.

=== Classification of bound morphemes ===
Bound morphemes can be further classified as derivational or inflectional morphemes. The main difference between them is their function in relation to words.

==== Derivational bound morphemes ====
* [[Derivation (linguistics)|Derivational]] morphemes, when combined with a root, change the semantic meaning or the [[part of speech]] of the affected word. For example, in the word ''happiness'', the addition of the bound morpheme ''-ness'' to the root ''happy'' changes the word from an [[adjective]] (''happy'') to a [[noun]] (''happiness''). In the word ''unkind'', ''un-'' functions as a derivational morpheme since it inverts the meaning of the root morpheme (word) ''kind''. Generally, morphemes that affix to a root morpheme (word) are bound morphemes.

==== Inflectional bound morphemes ====
* [[Inflection]]al morphemes modify the [[grammatical tense|tense]], [[aspect (linguistics)|aspect]], [[mood (linguistics)|mood]], [[personal pronoun#Person and number|person]], or [[number (linguistics)|number]] of a [[verb]] or the [[grammatical number|number]], grammatical [[gender (linguistics)|gender]], or [[case (linguistics)|case]] of a noun, adjective, or [[pronoun]] without affecting the word's meaning or class ([[part of speech]]). Examples of applying inflectional morphemes to words are adding ''-s'' to the root ''dog'' to form ''dogs'' and adding ''-ed'' to ''wait'' to form ''waited''. An inflectional morpheme changes the form of a word. English has eight inflections.<ref>{{cite web| url = https://faculty.unlv.edu/nagelhout/ENG411Bs12C/mod1concept2.html| archive-url = https://web.archive.org/web/20130218050235/http://faculty.unlv.edu/nagelhout/ENG411Bs12C/mod1concept2.html| archive-date = 2013-02-18| work= ENG 411B | title =Module 1 Concepts: Inflectional Morpheme }}</ref><ref>{{cite book |last1=Matthew |first1=Baerman |title=The Morpheme |date=2015 |publisher=Oxford University Press |location=Oxford University Press |isbn=978-0-19-959142-8 |page=8 |url=https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199591428.001.0001/oxfordhb-9780199591428-e-1?print=pdf |access-date=30 September 2019 |archive-date=16 June 2022 |archive-url=https://web.archive.org/web/20220616052307/https://www.oxfordhandbooks.com/view/10.1093/oxfordhb/9780199591428.001.0001/oxfordhb-9780199591428-e-1?print=pdf |url-status=live }}</ref>

===Allomorphs===
[[Allomorph]]s are variants of a morpheme that differ in form but are semantically similar. For example, the English plural [[marker (linguistics)|marker]] has three allomorphs: {{IPA|/-z/}} (''bug'''s'''''), {{IPA|/-s/}} (''bat'''s'''''), or {{IPA|/-ɪz, -əz/}} (''bus'''es'''''). An allomorph is a concrete realization of a morpheme, which is an abstract unit. That is parallel to the relation of an [[allophone]] and a [[phoneme]].

===Zero-morpheme===
{{Main|Zero morpheme}}
A zero-morpheme is a type of morpheme that carries [[semantics|semantic]] meaning, but is not realized in speech. A word with a zero-morpheme is analyzed as having the morpheme for grammatical purposes, but the morpheme is not realized in speech. They are often represented by /[[∅]]/ within [[gloss (annotation)|glosses]].<ref>{{Cite journal|last1=Gerner|first1=Matthias|last2=Ling|first2=Zhang|date=2020-05-06|title=Zero morphemes in paradigms|url=https://www.jbe-platform.com/content/journals/10.1075/sl.16085.ger|journal=Studies in Language. International Journal Sponsored by the Foundation "Foundations of Language"|language=en|volume=44|issue=1|pages=1–26|doi=10.1075/sl.16085.ger|s2cid=218935697|issn=0378-4177|access-date=2020-09-15|archive-date=2020-09-19|archive-url=https://web.archive.org/web/20200919195529/https://www.jbe-platform.com/content/journals/10.1075/sl.16085.ger|url-status=live|url-access=subscription}}</ref>

Generally, such morphemes have no visible changes. For instance, ''sheep'' is both the singular and the plural form of that noun; rather than taking the usual plural suffix ''-s'' to form hypothetical ''*sheeps'', the plural is analyzed as being composed of ''sheep + -∅'', the null plural suffix. The intended meaning is thus derived from the [[co-occurrence]] [[determiner]] (in this case, "some-" or "a-").<ref>{{cite web|last1=Dahl|first1=Eystein Dahl|last2=Fábregas|first2=Antonio|title=Zero Morphemes|url=https://oxfordre.com/linguistics/view/10.1093/acrefore/9780199384655.001.0001/acrefore-9780199384655-e-592|access-date=3 November 2019|website=Linguistics|year=2018|doi=10.1093/acrefore/9780199384655.013.592|isbn=978-0-19-938465-5|archive-date=3 November 2019|archive-url=https://web.archive.org/web/20191103023401/https://oxfordre.com/linguistics/view/10.1093/acrefore/9780199384655.001.0001/acrefore-9780199384655-e-592|url-status=live}}</ref>

In some cases, a zero-morpheme may also be used to contrast with other inflected forms of a word that contain an audible morpheme. For example, the plural noun ''cats'' in English consists of the root ''cat'' and the plural suffix ''-s,'' and so the singular ''cat'' may be analyzed as the root inflected with the null singular suffix -''∅''.<ref>{{Cite web |title=Null morpheme – Glottopedia |url=http://www.glottopedia.org/index.php/Null_morpheme |access-date=2022-06-15 |website=glottopedia.org |archive-date=2022-06-22 |archive-url=https://web.archive.org/web/20220622125205/http://www.glottopedia.org/index.php/Null_morpheme |url-status=live }}</ref>

===Content vs. function===
[[Content morpheme]]s express a concrete meaning or ''content'', and function morphemes have more of a grammatical role. For example, the morphemes ''fast'' and ''sad'' can be considered content morphemes. On the other hand, the suffix ''-ed'' is a function morpheme since it has the grammatical function of indicating [[past tense]].

Both categories may seem very clear and intuitive, but the idea behind them is occasionally more difficult to grasp since they overlap with each other.<ref>{{cite web|title=Morphology II|url=http://www.ling.upenn.edu/courses/Fall_1998/ling001/morphology2.html|access-date=10 April 2014|archive-date=16 March 2014|archive-url=https://web.archive.org/web/20140316184334/http://www.ling.upenn.edu/courses/Fall_1998/ling001/morphology2.html|url-status=live}}</ref> Examples of ambiguous situations are the [[preposition]] ''over'' and the [[determiner]] ''your'', which seem to have concrete meanings but are considered function morphemes since their role is to connect ideas grammatically.<ref name="language files">{{cite book|title=Language files: Materials for an introduction to language and linguistics|date=2011|publisher=Ohio State University Press|author=Department of Linguistics|edition=11th}}</ref> Here is a general rule to determine the category of a morpheme:
* Content morphemes include free morphemes that are nouns, [[adverbs]], [[adjectives]], or main verbs, as well as bound morphemes such as bound roots and derivational affixes.<ref name="language files" />
* Function morphemes may be free morphemes that are prepositions, [[pronoun]]s, determiners, auxiliary verbs or [[Conjunction (grammar)|conjunctions]], or bound morphemes that are inflectional affixes.<ref name="language files" />

==Other features==
Roots are composed of only one morpheme, but stems can be composed of more than one morpheme. Any additional affixes are considered morphemes. For example, in the word ''quirkiness'', the root is ''quirk'', but the stem is ''quirky'', which has two morphemes.

Moreover, some pairs of affixes have identical phonological form but different meanings. For example, the suffix ''-er'' can be either derivational (e.g. ''sell'' ⇒ ''seller'') or inflectional (e.g. ''small'' ⇒ ''smaller''). Such morphemes are called [[homophonous]].<ref name="language files" />

Some words might seem to be composed of multiple morphemes but are not. Therefore, not only form but also meaning must be considered when identifying morphemes. For example, the word ''Madagascar'' is long and might seem to have morphemes like ''mad'', ''gas'', and ''car'', but it does not. Conversely, some short words have multiple morphemes (e.g. ''dogs'' = ''dog'' + ''s'').<ref name="language files" />

== Morphological analysis ==
In [[natural language processing]] for [[Japanese language|Japanese]], [[Chinese language|Chinese]], and other languages, morphological analysis is the process of segmenting a sentence into a row of morphemes. Morphological analysis is closely related to [[part-of-speech tagging]], but word segmentation is required for those languages because word boundaries are not indicated by blank spaces.<ref>{{Cite book |last=Nakagawa |first=Tetsuji |chapter=Chinese and Japanese word segmentation using word-level and character-level information |date=2004 |title=Proceedings of the 20th international conference on Computational Linguistics - COLING '04 |chapter-url=http://portal.acm.org/citation.cfm?doid=1220355.1220422 |language=en |location=Geneva, Switzerland |publisher=Association for Computational Linguistics |pages=466–es |doi=10.3115/1220355.1220422|s2cid=2988891 |doi-access=free }}</ref>

The purpose of morphological analysis is to determine the minimal units of meaning in a language (morphemes) by comparison of similar forms: such as comparing "She is walking" and "They are walking" with each other, rather than either with something less similar like "You are reading". Those forms can be effectively broken down into parts, and the different morphemes can be distinguished.

Both meaning and form are equally important for the identification of morphemes. An agent morpheme is an affix like ''-er'' that in English transforms a verb into an agent noun (e.g. ''teach'' → ''teacher''). English also has another morpheme identical in pronunciation (and written form) but with unrelated meaning and function: a comparative morpheme that changes the positive form of an adjective to another degree of comparison (but remains the same adjective) (e.g. ''small'' → ''smaller''). The opposite can also occur: a pair of morphemes with identical meaning but different forms.<ref name="language files" />

==Changing definitions==
{{Unreferenced section|date=September 2011}}
In [[generative grammar]], the definition of a morpheme depends heavily on whether syntactic trees have morphemes as leaves or features as leaves.
* Direct surface-to-[[syntax]] mapping in [[lexical functional grammar]] (LFG) – leaves are words
* Direct syntax-to-semantics mapping
** Leaves in syntactic trees spell out morphemes: [[distributed morphology]] – leaves are morphemes
** Branches in syntactic trees spell out morphemes: radical minimalism and [[nanosyntax]] – leaves are "nano-" (small) morpho-syntactic features

Given the definition of a morpheme as "the smallest meaningful unit", nanosyntax aims to account for idioms in which an entire syntactic tree often contributes "the smallest meaningful unit". An example [[idiom]] is "Don't let the cat out of the bag". There, the idiom is composed of "let the cat out of the bag". That might be considered a semantic morpheme, which is itself composed of many syntactic morphemes. Other cases of the "smallest meaningful unit" being longer than a word include some collocations such as "in view of" and "business intelligence" in which the words, when together, have a specific meaning.

The definition of morphemes also plays a significant role in the interfaces of generative grammar in the following theoretical constructs:
* [[Event semantics]]: the idea that each productive morpheme must have a compositional semantic meaning (a [[denotation]]), and if the meaning is there, there must be a morpheme (whether [[null morpheme|null]] or overt).
* [[Spell-out]]: the interface with which syntactic/semantic structures are "spelled out" by using words or morphemes with phonological content. That can also be thought of as lexical insertion into the syntactic.

== See also ==
* {{annotated link|Alternation (linguistics)}}
* {{annotated link|Floating tone}}
* {{annotated link|Hybrid word}}
* {{annotated link|List of Greek morphemes used in English}}
* {{annotated link|Morphological parsing}}
* {{annotated link|Morphophonology}}
* {{annotated link|Morphotactics}}
* ''{{annotated link|Motif-Index of Folk-Literature}}'', featuring a comparable concept in folklore studies
* {{annotated link|Theoretical linguistics}}
* {{annotated link|Word stem}}

== References ==
{{Reflist}}
{{refbegin}}
* {{citation <!--The Oxford Handbook of Inflection--> | first=Matthew |last=Baerman  |year=2015 | title=The Morpheme <!--| chapter=https://www-oxfordhandbooks-com.ezproxy3.library.arizona.edu/view/10.1093/oxfordhb/9780199591428.001.0001/oxfordhb-9780199591428-e-1?print=pdf--> | editor=Matthew Baerman  | others=Stephen R. Anderson | page=3 | location=Oxford University| publisher=Oxford University Press | id= | url=https://www-oxfordhandbooks-com.ezproxy3.library.arizona.edu/view/10.1093/oxfordhb/9780199591428.001.0001/oxfordhb-9780199591428-e-1?print=pdf }}{{dead link|date=January 2024}}
* {{citation <!--Introduction to English Linguistics--> | first=Ingo |last=Plag  |year=2015 | title=The structure of words: morphology | others=Sabine Arndt-Lappe, Maria Braun, and Mareile Schramm | pages=71–112 | location=Berlin, Germany| publisher=De Gruyter, Inc.}}
{{refend}}

== External links ==
{{Wiktionary|morpheme}}
* [https://web.archive.org/web/20070523063957/http://www.educationoasis.com/curriculum/Reading/glossary_reading_terms.htm Glossary of reading terms]
* [http://www.prefixsuffix.com/ Comprehensive and searchable morpheme reference]
* [http://www.ling.upenn.edu/courses/Fall_2007/ling001/morphology.html Linguistics 001 —  Lecture 7 —  Morphology] by Mark Lieberman
* [http://cougar.eb.com/soundc11/m/morphe01.wav Pronunciation of the word morpheme] {{Webarchive|url=https://web.archive.org/web/20110717120826/http://cougar.eb.com/soundc11/m/morphe01.wav |date=2011-07-17 }}

{{Lexicology}}
{{Lexicography}}
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[[Category:Morphemes]]
[[Category:Learning to read]]
[[Category:Linguistics terminology]]
[[Category:Reading (process)]]