1. A romantic relationship between two people that is committed, stable, and involves deep emotional connection and long-term intentions
After dating for a year, they decided to have a serious relationship.
Depois de namorar por um ano, eles decidiram ter um relacionamento sério.
2. A partnership characterized by exclusivity, trust, and potential future commitment such as marriage
She was looking for a serious relationship, not just casual dating.
Ela estava procurando um relacionamento sério, não apenas namorar casualmente.