Memory loss. You often repeat yourself in conversations because you don't remember having said something prior. You forget names, dates, things you're supposed to do, etc. There's medications that can slow the process but not stop or reverse it.
Problems with memory, behavior/emotions, language problems (like forgetting object names for example), losing interest in normal activities you do. There's many symptoms of Dementia. It depends on how severe it is.
Memory loss. This is usually the earliest and most noticeable symptom. Trouble recalling recent events or recognizing people and places. Trouble finding the right words. Problems planning and carrying out tasks, such as balancing a checkbook, following a recipe, or writing a letter. Trouble exercising judgment, such as knowing what to do in an emergency. Trouble controlling moods or behaviors. Depression is common, and agitation or aggression may occur. Not keeping up personal care such as grooming or bathing. http://www.webmd.com/alzheimers/tc/dementia-symptoms