Questions & Answers about O cachorro é rápido.
O is the masculine singular definite article, meaning the. It goes with cachorro because cachorro is a masculine singular noun.
- o cachorro = the dog
- um cachorro = a dog
So O cachorro é rápido means The dog is fast, not A dog is fast.
In Portuguese, many nouns have grammatical gender. Cachorro is the masculine form for dog, and cachorra is the feminine form.
- o cachorro = the male dog / the dog (masculine)
- a cachorra = the female dog
If you change the noun to the feminine form, the article and adjective usually change too:
- A cachorra é rápida.