充填

1. Origins, structure, and basic meaning

• Structure: 充填 (じゅうてん) is a verbal noun for filling an empty space with material. 充填する is active, while 充填されている presents the resulting filled state.
• Basic usage: A procedure uses 充填する前 before liquid is put into a container; a description of material occupying a gap uses 充填されている.

2. Common pitfalls and similar expressions

• Filling operation versus filled state
  • 充填する focuses on the operation, but 充填されている focuses on the affected space and its continuing condition. The passive form does not describe an active operation in progress.