Through the joys of Pinterest, I chanced upon a post at Disability and Media Matters in which the author questions when he stopped being considered "Dad" or "Father" to people who inquire about his special needs son, and instead became "carer." I think he raises a very good question and one I wanted to consider.
Lyn's diagnosis with early on-set Alzheimer's has brought the term "caregiver" into our vocabulary. Unlike the author linked above, we had not previously been asked if we were her "carer." She was referred to as our "daughter" or "sister" and we as her "mother" or "sister." According to the definition of a care giver, we've actually been her family and her carers her entire life. This is especially true of Mom because Mom has tended to Lyn's daily needs since birth. While Mom hasn't had to dress her, bathe her or help her with toilet needs all this time, she had advocated for Lyn with physicians, petitioned for legal guardianship and managed a household in which Lyn comfortably resides.
Caregiver was not part of how we described our relationship with Lyn until just recently. While we are still Mom and sister, we have also assumed the title of caregiver because her needs have changed. For me, I think the difference is the terminal nature of her diagnosis. We are there to help her and hold her hand as her body and mind fail. That is what made the difference in my mind.