Grammar class or word class is the name given to the set that classifies a word, based on its syntactic and morphological structure.
In Portuguese, there are ten grammatical classes, which are subdivided into variable and invariant grammatical classes.
At variable part of speech are known by: noun, adjective, numeral, pronoun, verb and article.
already the invariant grammar classes they are constituted by: adverb, conjunction, interjection and adpositions (proposition, postposition and circumposition).
When it is said that a grammatical class is variable, it means that it has the ability to be inflected, that is, to assume the form of plural or singular, male or female, and so on.
The invariables, on the other hand, are static, that is, they do not undergo flexion in their structures.
Morphology is the field of study specializing in grammatical classes, that is, how words are formed and their syntactic and morphological characteristics.
Learn more about the meaning of Morphology and definite and indefinite article.
| Class | Function / Feature |
| Substantive | Words that name things, beings, places. They can be inflected into "gender", "number" and "degree". |
| Verb | Words that indicate an action, state, occurrence or phenomenon. They can be inflected into "number", "voice", "person", "mode", "time" and "aspect". |
| Adjective | Words that characterize or qualify the nouns. They can be inflected into "gender", "number" and "degree". |
| Adverb | Words that alter a verb, an adjective, or another adverb. They are invariable, but some adverbs can be inflected to "degree". |
| Pronoun | Words that replace, accompany, determine or modify some nouns in sentences. They can be inflected into "gender", "number" and "person". |
| Preposition | Words that make connections between two terms in a sentence. |
| Article | Words that precede the nouns, defining them or not. Can be inflected into "gender" and "number". |
| Interjection | Words that express emotions, sensations or moods. They are invariable. |
| Conjunction | Words that serve as linking elements between two clauses or terms of the same clause. They are invariable. |
| Numeral | Words that indicate quantities, whether of people, things, etc. Can be inflected into "gender" and "number". |