断言

1. Origins, structure, and basic meaning

• Structure: 断言 (だんげん) denotes a firm assertion and forms the verb to declare categorically.
• Basic usage: 成功だと断言できない rejects an unsupported conclusion; 完成させると断言した reports a firm promise.

2. Common pitfalls and similar expressions

• Quoted claim and modal contrast
  • The asserted proposition is marked by と. できない denies the ability to assert it, while した reports an actual declaration.