1. A formal, sincere, and earnest statement or announcement made with genuine intent and conviction
The politician made a serious declaration about the new environmental policy.
O político fez uma declaração séria sobre a nova política ambiental.
2. A solemn or legally binding statement of facts, intentions, or commitments
She made a serious declaration of her commitment to the project.
Ela fez uma declaração séria de seu compromisso com o projeto.