Grief is the response to loss, particularly to the loss of someone or some living thing that has died, to which a bond or affection was formed. Although conventionally focused on the emotional response to loss, grief also has physical, cognitive, behavioral, social, cultural, spiritual and philosophical dimensions. While the terms are often used interchangeably, bereavement refers to the state of loss, while grief is the reaction to that loss.

The grief associated with death is familiar to most people, but individuals grieve in connection with a variety of losses throughout their lives, such as unemployment, ill health or the end of a relationship. Loss can be categorized as either physical or abstract; physical loss is related to something that the individual can touch or measure, such as losing a spouse through death, while other types of loss are more abstract, possibly relating to aspects of a person's social interactions.