婚約

1. Origins, structure, and basic meaning

• Structure: 婚約 (こんやく) is the noun engagement and the stem used in 婚約する, to become engaged.
• Basic usage: 婚約を報告する reports an engagement as a fact, while 友人と婚約した predicates becoming engaged to a partner.

2. Common pitfalls and similar expressions

• Nominal 婚約 and verbal 婚約した
  • The engagement takes を as the thing reported, whereas the partner is linked by と in the verbal construction.