固まる

1. Origins, structure, and basic meaning

• Structure: 固まる(かたまる) is an intransitive verb for becoming firm or coming together in a mass.
• Basic usage: Its interpretation depends on the subject, from gelatin setting to people gathering in one place.

2. Common pitfalls and similar expressions

• 固まる and 固める
  • ゼリーが固まる describes the gelatin changing; ゼリーを固める describes making it set. 固める(かためる) takes を for the object being changed.
• When people are the subject
  • 参加者が入口付近に固まった means that the participants clustered near the entrance. It emphasizes clustering in one spot more than the simpler 集まる(あつまる).