What word can describe a lack of care or attention?

The word that aptly describes a lack of care or attention is "neglect." This term specifically refers to the failure to provide necessary care or the act of disregarding something that requires attention. In various contexts, neglect can apply to responsibilities, relationships, or tasks, indicating an absence of effort, interest, or concern.

In contrast, the other words have different meanings. "Commemorate" refers to honoring or remembering something or someone, often through a ceremony. "Ameliorate" means to improve or make something better, which is quite the opposite of showing a lack of care. "Resuscitate" involves bringing someone back to life or reviving them, particularly in a medical context, and does not relate to carelessness or inattention. Thus, "neglect" is the most fitting choice.