noun
General term for ink used in pens, printing, stamps, etc. A common everyday loanword.
万年筆のインクが切れた。
The fountain pen ran out of ink.
このプリンターはインクの減りが早い。
This printer runs out of ink quickly.
墨 refers to traditional Japanese/Chinese ink (sumi), often in solid stick form used for calligraphy and painting, while インク is the modern Western-style liquid ink.
Borrowed from English 'ink'.