In the wake of a death we use the term “grief” to describe what we and/or others are going through. The word “grief” seems to be an umbrella term that covers a variety of things happening with those closest to the person who has died. (Grief also extends to a variety of other life situations as well, but in the context of this site, I will focus on grief relating to the death of a loved one.) 
The Mayo Clinic website describes grief as “a strong, sometimes overwhelming emotion for people, regardless of whether their sadness stems from the loss of a loved one or from a terminal diagnosis they or someone they loved have received.”
Web MD defines grief as “your emotional reaction to a significant loss,” and associates grief most commonly with the terms “sorrow and heartache.” The site continues to describe the grieving process, as “the process of emotional and life adjustment you go through after a loss.”
The Hospice Foundation of America calls grief simply “a reaction to loss.”
And The Center for Loss and Life Transition writes that grief is “whatever you think and feel inside about death,” that includes “a combination of feelings such as shock, confusion, anxiety, anger, regret, and sadness.”
In and of itself, the definition of “grief” seems straightforward: it is a person’s emotional response to a loss, such as the death of a loved one. Grief also comes with physical and spiritual responses as well (subjects of upcoming Grief 101 posts).
From my experience of grief, I would describe the grief process as the process through which the griever adjusts to life without the physical and emotional presence of the loved one who has died.
A.N.Carroll 