harden · firm

1. Origins, structure, and basic meaning

• Structure: 固 is associated with becoming hard or firm; its on-reading is こ.
• Basic usage: 固まる(かたまる) means to harden, while 固める(かためる) means to make something hard or firm. ゼリーが固まった means that the jelly set, and 果汁を固めた means that someone made the fruit juice set.

2. Common pitfalls and similar expressions

• Gathering together and settling a policy
  • 参加者が入口付近に固まった means that the participants gathered together near the entrance. With people, the verb can describe clustering in one place.
  • 今後の方針を固める means settling a policy for the future. 固める is used for making a still-unsettled policy firm through repeated discussion.