thick · great

1. Origins, structure, and basic meaning

• Structure: 太 is associated with being large or thick; its kun-readings include ふとい and ふとる.
• Basic usage: 太い(ふとい) describes thickness, while 太る(ふとる) means to gain weight or grow thicker.

2. Common pitfalls and similar expressions

• Thickness and becoming thicker
  • 太い鉛筆 means a thick pencil. 太い also describes a pillar's thickness compared with an arm.
  • 幹が太ってきた means that a trunk has grown thicker. 太る applies to a plant's trunk growing thicker as well as to a person gaining weight.