jì​hao HSK7

mark

记号 (記號) jì​hao
mark noun
a visible sign, symbol, or imprint used for identification, recognition, or as a reminder

He folded the corner of that page as a mark.

notation noun
a system of characters or specialized symbols used to represent information in fields like music or mathematics

This kind of mathematical notation is very common in textbooks.

Frequency

Movie subtitles
7.48 per million appears in 3% of films
Written text
1.81 per million

Details

HSK 3.0
Level 7

Sources

Definitions
CC-CEDICT