1. to notice or perceive something and register it as being significant
I observed that she seemed nervous during the presentation.
Observei que ela parecia nervosa durante a apresentação.
2. to watch carefully, especially with attention to details or behavior for the purpose of arriving at a judgment
The scientist observed the bacteria under the microscope.
O cientista observou as bactérias sob o microscópio.
3. to comply with or follow a law, custom, practice, or agreement
All citizens must observe traffic laws.
Todos os cidadãos devem observar as leis de trânsito.