The preterite is used to express past actions that have been completed. They are often contrasted with another action that is taking place in the background when an event occurs. We often use the imperfect to set the background and context in which an action took place, and the action is expressed in the Past Definite (simple past).
- Eles assistiam televisão quando o telefone tocou. [ They were watching television when the phone rang. ]
- Eu estudei Português ontem. [ I studied Portuguese yesterday. ] (When you use a word like yesterday, which pinpoints a definite time, you use the past definite).
- Ontem falei com Mary. [ Yesterday I talked to Mary. ]
- Ele trabalhou semana passada. [ He worked last week. (Last week is a definite time). ]
- Ele não trabalhou semana passada. [ He did not work last week. ]
- Choveu ontem à noite. [ It rained last night. ]
- Ela vendeu o carro. [ She sold the car. ]
- Abrimos a loja. [ We opened the store. ]
With many thanks to my collaborator Mat Pestana.