What 绪 means
A thread end branches into beginnings, clues, and thought.
An early form, catalogued as 包2.263, appears in a manuscript from ancient Chu, a Chinese state during the Warring States period; it was found in a Baoshan tomb dated 316 BCE. The Eastern Han dictionary Shuowen defines 緒 as the end of a silk thread; 糸 carries the meaning and 者 the sound.
绪 is simplified; 緒 is traditional, and 緖 is a variant form.
Alone, 绪 leaves several senses open; the compound settles it.
“Emotion” is only one possible sense.
What it means when someone sends it to you
4 readingsQuestions people ask
1Why does 绪 show as a box on some devices?
Because that device's fonts have no glyph for it. The character is still correct and still copies correctly — the box is a missing glyph, not a broken character.
How to type 绪
绪\7EEACodes and encoding1 code points
A visible symbol can contain several code points. JS .length counts UTF-16 units; UTF-8 counts bytes.

