1. The simplest or most fundamental form of a word, typically the infinitive for verbs or the singular for nouns, from which other forms are derived
The base form of 'running' is 'run'.
A forma base de 'correndo' é 'correr'.
2. In linguistics and grammar, the root or citation form of a word that appears in dictionaries
The base form of the verb appears in the dictionary as the entry word.
A forma base do verbo aparece no dicionário como a palavra de entrada.