fill

1. Origins, structure, and basic meaning

• Structure: 充 expresses filling or making something substantial and has the on-reading じゅう.
• Basic usage: 充電(じゅうでん) means charging, while 充実(じゅうじつ) describes something well supplied or fulfilling.

2. Common pitfalls and similar expressions

• A rich collection and fulfilling time
  • 資料が充実していて describes a well-stocked collection, while 充実した一日 is a fulfilling day. 充実した modifies the following 一日.