意外

1. Origins, structure, and basic meaning

• Structure: 意外 (いがい) marks surprise when reality differs from expectation. The examples use a predicate and emphatic adverbial form.
• Basic usage: A quiet person's singing ability is surprising; unexpectedly, a meeting ends early.

2. Common pitfalls and similar expressions

• Judgment of a surprising fact and adverb modifying an event
  • 意外だった evaluates a nominalized fact; 意外にも scopes over the following event. An expectation baseline is required.