Phi features is a linguistic term used to describe the semantic features of person, number and gender, as encoded in such words 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), which can be used to describe lexical categories and case features.[1]
When written, the symbol φ is used to represent 'phi'.