Indelible ink is a type of ink that cannot be easily erased or removed. It is typically used for marking items or for voting purposes. There are a number of synonyms for indelible ink, including permanent ink, durable ink, steadfast ink, unfading ink, and imperishable ink. Each of these terms emphasizes the ink's ability to remain in place and resist fading, making it an ideal choice for important documents and records. Some other closely related terms include non-removable ink and unerasable ink, both of which emphasize the ink's resistance to erasure or removal without damage to the underlying material.