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Xu, H. Phi Features. Encyclopedia. Available online: (accessed on 04 December 2023).
Xu H. Phi Features. Encyclopedia. Available at: Accessed December 04, 2023.
Xu, Handwiki. "Phi Features" Encyclopedia, (accessed December 04, 2023).
Xu, H.(2022, October 26). Phi Features. In Encyclopedia.
Xu, Handwiki. "Phi Features." Encyclopedia. Web. 26 October, 2022.
Phi Features

In linguistics, especially within generative grammar, phi features (denoted with the Greek letter φ 'phi') are the semantic features of person, number, gender, and case, as encoded in pronominal agreement with nouns and pronouns (the latter are said to consist only of phi-features, containing no lexical head). Several other features are included in the set of phi-features, such as the categorical features ±N (nominal) and ±V (verbal), which can be used to describe lexical categories and case features. Phi-features are often thought of as the "silent" features that exist on lexical heads (or, according to some theories, within the syntactic structure) that are understood for number, gender, person or reflexivity. Due to their silent nature, phi-features are often only understood if someone is a native speaker of a language, or if the translation includes a gloss of all these features. Many languages exhibit a pro-drop phenomenon which means that they rely on other lexical categories to determine the phi-features of the lexical heads.

lexical categories semantic features categorical features

1. Predicate-Argument Agreement

Chomsky first proposed that the N node in a clause carries with it all the features to include person, number and gender[1]. In English, we rely on nouns to determine the phi-features of a word, but some other languages rely on inflections of the different parts of speech to determine person, number and gender of the nominal phrases to which they refer. Mainly verbs and adjectives are responsible for bearing inflections which signal the phi-features of a particular subject or object. Verbs appear to be responsible for carrying the most features and tend to carry person, number and gender agreements cross-linguistically for both subjects and objects[2]. Adjectives also carry phi-features in some languages, however, they tend to agree in number and gender but rarely for person[2].

1.1. Person

In English, person agreement is understood in the pronoun or noun overtly, while the verb carries the agreement marker to agree with the person phi-features on the noun. For English, there is only one verb agreement required for the third person singular in the present tense (usually -s), as seen in the table[3]:

  singular plural
1st I walk We walk
2nd You walk You (all) walk
3rd He/she/it walks They walk

In a null-subject language such as Italian, however, pronominal subjects are not required (in fact, in many null subject languages, producing overt subjects is a sign of non-nativity). These type of "unstressed" pronouns are called clitic pronouns. Therefore, Italian uses a different inflectional morphology on verbs that is based on the person features of the nominal subject it agrees with[4]:

- Camminare (to walk):

cammino (I walk), camminiamo (we walk)

cammini (you walk), camminate (you all walk)

cammina (he/she walks), camminano (they walk)

1.2. Number

The grammatical term number is the name of the system contrasting singular and plural[5]. In English, number agreement is not expressed through agreement of verbal elements like they are in other languages. This is partly because English is a language that requires subjects and the subjects in English overtly express number. Instead, English number is a phi-feature that is inflected on nouns when the nominal phrase is plural. The most common in English is -s inflected on nouns that are plural:

- Ducks, fridges, baseballs, cups, books, mirrors, cars, buildings, clowns, bridges, creams....

Some cases of plurality in English require conjugation of the entire noun to express the phi-feature of plurality:

- Men, women, mice, teeth....

Neither verbs nor adjectives are used to agree with the number feature of the noun that they are agreeing with in English.

Some languages, however, like Salish Halkomelem, differ from English in their syntactic categorization of plural marking. Halkomelem allows for both marked and unmarked plural forms of its' nouns. It also allows for the determiners to be marked or unmarked in their plurality. Plural nouns and determiners in Halkomelem can be freely combined as well, but it appears that if a determiner is plural in a phrase it is sufficient to pluralize the noun that it modifies[6]:

Plurality in Salish Halkomelem
    noun determiner translation
unmarked   swíyeqe te man (plural OR singular)
marked   swí:wíqe ye men (plural only)

1.3. Gender

English is a language that does not have nominal phrases that belong to a gender class where agreement of other elements in the phrase is required. Dutch is another language that only differentiates between neuter and the common gender[7]. Many other languages of the world do have gender classes. German, for example, has three genders; feminine, masculine and neuter[7]. For a Romance language like Italian, there are feminine and masculine genders. Inflections on the adjectives and determiners are used for gender agreement within the pronominal phrase[8].

English only expresses gender when the pronoun addresses a specific person who semantically belongs to a certain gender. See the table below for Pronominal Case Forms in English under 3 sg. fem/masc.

1.4. Case

The phi-feature of case is explicit in English only for pronominal forms (see the picture of the table for Pronominal Case Forms in English). English is not a language that has inflectional case forms for proper nouns.

The bolded forms show the irregular pattern.

German is language that exhibits some inflectional case forms on nouns[9]. It also obligatorily displays case forms on its' determiners:

  sing plural
nom der die
acc den die
gen des der
dat dem den

Case in terms of reflexivity is overt in English for every person (see the table for Pronominal Case Forms in English):

myself, yourself, himself, herself,yourselves, ourselves, themselves

The pattern for the reflexive form of the third person masculine pronoun does not follow the same pattern of reflexivity as the other pronouns in terms of case form marking for pronominal English.

In many languages, reflexivity is not overt for person. A prime example is apparent in French se. French se is used to express reflexivity for every expression of the third person, regardless of gender or person. It also functions as a middle, an inchoative, an applicative and an impersonal. For this reason, some theories suggest that reflexive phi-features for languages such as French posit in a level on the syntactic structure that is silent, between the determiner and the noun. This creates a new "silent" projection to a node specifically for φ-reflexives in French structure[10].

2. Categorical Features

Phi-features can also be considered the silent features that determine whether a root word is a noun or a verb. This is called the noun-verb distinction of Distributed Morphology. The table below describes how category classes are organized by their Nominal or Verbal characteristics. Definitions for these four categories of predicates have been described as follows:

A verbal predicate has a predicative use only; a nominal predicate can be used as the head of a term; an adjectival predicate can be used as a modifier of a nominal head; a preposition acts as a term-predicate for which the noun is still the head; an adverbial (not shown below) predicate can be used as a modifier of a non-nominal head.[11]

  + N - N
+ V +V +N


+V -N


- V -V +N


-V -N


X-bar theory approaches categorical features in this way: when a head X selects its' complement to project to X', the XP that it projects to then is a combination of the head X and all of its' categorical features, those being either nominal, verbal, adjectival or prepositional features[12]. It has also been argued that adpositions (cover term for prepositions and postpositions[13]) are not part of the [+/-N] [+/-V] system as shown above. This is because they resist being part of a single class category, like nouns, verbs and adjectives do. This argument also posits that some appositions may behave as part of this type of categorization, but not all of them do.


There are three main hypotheses regarding the syntactic categories of words. The first one is the Strong Lexical hypothesis, which states that verbs and nouns are inherent in nature, and when a word such as "walk" in English can surface as either a noun or a verb, depending on the speaker's intuitions of what the meaning of the verb is[14]. This means that the root "walk" in English has two separate lexical entries[15]:

walk N <[AP]> an act or instance of going on foot especially for exercise or pleasure[16]

walk V <[DPtheme]> to move along on foot : advance by steps[17]

2.1. Syntactic Analysis

Left is the environment for categorizing a noun; right is the environment for verb categorization.
"The verbalizing head takes as its complement a structure that already contains a noun"[18].

This analysis states that the category is determined by syntax or context. A root word is inserted into the syntax as bare and the surrounding syntax determines if it will behave as a verb or a noun. Once the environment has determined its' category, morphological inflections also surface on the root according to the determined category. Typically, if the element before it is a determiner, the word will surface as a noun, and if the element before it is a tense element, the root word will surface as a verb[19]. The example in the photo shows an example from Italian. The root of the word is cammin- ("walk"). This word could surface as either a noun or verb. The first tree shows that when the element before is a D "una", the root will be an N and the following morphology will inflect -ata which is the correct full orthography for the noun "walk" in Italian. The tree on the right shows a similar process but in the environment where the root follows a tense element, and the morphology inflects -o as a suffix, which makes the verb surface not only as a verb, but as discussed before in person agreement, also shows that this is the first person present form of the verb ("I walk").

2.2. Combinatorial Analysis

Syntactic decomposition for categorization of parts of speech includes an explanation for why some verbs and nouns have a predictable relationship to their nominal counterparts and why some don't. It says that the predictable forms are denominal and that the unpredictable forms are strictly root-derived[20]. The examples provided are of the English verbs hammer and tape. A verb such as hammer is a root-derived form, meaning that it can appear within an NP or within a VP. A denominalized verb, such as tape must first be converted from an NP because its' meaning relies on the semantics of the noun[21].

The discussion of how categorical features are determined is still up for debate and there have been numerous other theories trying to explain how words get their meanings and surface in a category. This is an issue within categorical distinction theories that has not yet come to a conclusion which is agreed upon in the linguistic community. This is interesting because phi-features in terms of person, number and gender are concrete features that have been observed numerous times in natural languages, and are consistent patterns that are rooted in rule-based grammar.


  1. Noam., Chomsky (1965). Aspects of the theory of syntax. Cambridge: M.I.T. Press. ISBN 978-0262530071. OCLC 309976.
  2. Baker, Mark C. (2008). The Syntax of Agreement and Concord. Cambridge: Cambridge University Press. doi:10.1017/cbo9780511619830. ISBN 9780511619830.
  3. Pullum, Geoffrey K.; Huddleston, Rodney (2002) (in en). The Cambridge Grammar of the English Language by Rodney Huddleston. doi:10.1017/9781316423530. ISBN 9781316423530. Retrieved 2018-12-17. 
  4. CHAMBERS, BETTYE (2008). "A Reference Grammar of Modern Italian. 2nd ed. by MAIDEN, MARTIN, & CECILIA ROBUSTELLI". The Modern Language Journal 92 (4): 661–663. doi:10.1111/j.1540-4781.2008.00793_19.x. ISSN 0026-7902.
  5. Huddleston, Rodney; Payne, John (2002) (in en). The Cambridge Grammar of the English Language. pp. 323–524. doi:10.1017/9781316423530.006. ISBN 9781316423530. Retrieved 2018-12-14. 
  6. Wiltschko, Martina (2008). "The Syntax of Non-Inflectional Plural Marking on JSTOR" (in en). Natural Language & Linguistic Theory 26 (3): 639–694. 
  7. Dikken, Marcel den (2011-11-01). "Phi-feature inflection and agreement: An introduction" (in en). Natural Language & Linguistic Theory 29 (4): 857–874. doi:10.1007/s11049-011-9156-y. ISSN 1573-0859.
  8. CHAMBERS, BETTYE (2008). "A Reference Grammar of Modern Italian. 2nd ed. by MAIDEN, MARTIN, & CECILIA ROBUSTELLI". The Modern Language Journal 92 (4): 661–663. doi:10.1111/j.1540-4781.2008.00793_19.x. ISSN 0026-7902.
  9. "Toms Deutschseite - Demonstrativpronomen". 
  10. Déchaine, Rose-Marie; Wiltschko, Martina (2017-03-23). "A Formal Typology of Reflexives" (in en). Studia Linguistica 71 (1–2): 60–106. doi:10.1111/stul.12072. ISSN 0039-3193.
  11. Denmark), Functional Grammar Conference (1990 : Copenhagen (1992). Layered structure and reference in a functional perspective papers from the Functional Grammar Conference in Copenhagen, 1990. John Benjamins Pub. ISBN 9789027282903. OCLC 929632129.
  12. Kerstens, Johan (2012-06-25) (in en). The Syntax of Number, Person and Gender: A Theory of Phi-Features. Walter de Gruyter. ISBN 9783110869361. 
  13. "Adposition" (in en). 2015-12-03. 
  14. Vigliocco, Gabriella; Vinson, David P.; Druks, Judit; Barber, Horacio; Cappa, Stefano F. (2011). "Nouns and verbs in the brain: A review of behavioural, electrophysiological, neuropsychological and imaging studies". Neuroscience & Biobehavioral Reviews 35 (3): 407–426. doi:10.1016/j.neubiorev.2010.04.007. ISSN 0149-7634. PMID 20451552.
  15. Linzen, Tal (December 11, 2018). "Syntactic Categories as Lexical Features or Syntactic Heads: An MEG Approach". 
  16. "Definition of WALK" (in en). 
  17. "Definition of WALK" (in en). 
  18. Phoevos, Panagiotidis. Categorial features : a generative theory of word class categories. Cambridge. ISBN 9781316190968. OCLC 896908624.
  19. Marantz, Alec (1997). "No Escape from Syntax: Don't Try Morphological Analysis in the Privacy of Your Own Lexicon". U. Penn Working Papers in Linguistics 4: 201–205. 
  20. Kiparsky, Paul (1982). "Word Formation and the Lexicon". Proceedings of the Mid-America Linguistics Conference: 3–29. 
  21. Arad, Maya (2003). "Locality Constraints on the Interpretation of Roots: The Case of Hebrew Denominal Verbs". Natural Language and Linguistic Theory 21 (4): 737–778. doi:10.1023/a:1025533719905. ISSN 0167-806X.
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