India ink or Chinese ink: the black liquid used in calligraphy and painting.
書道の授業で墨汁を使って半紙に字を書いた。
In calligraphy class I used ink to write characters on hanshi paper.
服に墨汁をこぼしてしまって、なかなか落ちない。
I spilled ink on my clothes, and it won't come out easily.
この画材店は品質の良い墨汁を扱っている。
This art supply store carries high-quality ink.
The black ink produced by cephalopods (e.g., squid or cuttlefish); sometimes used in cooking (e.g., squid ink pasta).
イカ墨のパスタは、墨汁を使った料理の代表例だ。
Squid-ink pasta is a representative dish that uses squid ink.
新鮮な鱈（たら）にイカの墨汁を少し加えてソースを作った。
I made a sauce for fresh cod by adding a little squid ink.