随意

1. Origins, structure, and basic meaning

• Structure: 随意 (ずいい) is a noun and na-adjectival expression meaning that something is left to individual choice rather than imposed.
• Basic usage: The form 随意に appears in formal instructions and administrative contexts with the sense at will or optionally.
  • 見学後は随意に解散してください。 — After the tour, you are free to leave individually.
  • 参加者は三つの課題から一つを随意に選べる。 — Participants may choose any one of the three assignments.

2. Common pitfalls and similar expressions

• Choice versus randomness
  • 随意 means according to one's own choice, not randomly. It sounds more formal and written than everyday 自由に.