垂直线

• 土(earth; soil; land)RADICAL
• 垂(hang down; droop)ASSOCIATIVE

Branches and leaves drooping down to touch the ground show the image of the character meaning to hang or droop.

• 十(ten; vertical)ASSOCIATIVE
• 目(eye)RADICAL
• 一(one; straight line)ASSOCIATIVE

An eye looking straight down one line without deviation is what makes something upright and straightforward.

• 糸(thread; silk)RADICAL
• 泉(stream; water)PHONETIC

A thin thread flows like a small stream running long and continuously.