容易

1. Origins, structure, and basic meaning

• Structure: 容易, read ようい, is a na-adjectival stem meaning easy or readily accomplished.
• Basic usage: 容易に組み立てられる adverbially describes assembly; 容易ではなかった negates ease in the past.

2. Common pitfalls and similar expressions

• Adverbial 容易に and negative predicate
  • に modifies an action, while ではなかった gives a past negative judgment about the task's difficulty.