“mark / seal” in Japanese is 印, read in, shirushi (いん, しるし). It is a Grade 4 Kyōiku kanji, taught in year 4 of Japanese elementary school, and appears in words such as 印鑑 (seal / stamp).
What does 印 mean?
大事な所に印をつける。
Same sound, different character — the classic trap. Compare them side by side: