Phi features is a linguistic

Linguistics

Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

 term to describe the semantic features of person

Grammatical person

Grammatical person, in linguistics, is deictic reference to a participant in an event; such as the speaker, the addressee, or others. Grammatical person typically defines a language's set of personal pronouns...

, number

Grammatical number

In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions ....

 and gender

Grammatical gender

Grammatical gender is defined linguistically as a system of classes of nouns which trigger specific types of inflections in associated words, such as adjectives, verbs and others. For a system of noun classes to be a gender system, every noun must belong to one of the classes and there should be...

, as encoded in words such as nouns and pronouns (which 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) that can be used to describe lexical categories

Lexical category

In grammar, a part of speech is a linguistic category of words , which is generally defined by the syntactic or morphological behaviour of the lexical item in question. Common linguistic categories include noun and verb, among others...

and the Case features.

When written, the symbol φ is used to represent 'phi'.