Melena (Greek melas = black) is a medical term for black tarry stool due to blood in the stool, usually originating from the upper gastrointestinal tract (stomach or above).

The term is sometimes publicly (but not medically) used for a black vomit.  

It is important to differ between melena and black bowel movement from reasons, other than bleeding.

Color of normal bowel movement in most people is any shade of brown, including the light brown (described as yellow by some, but this is  not the same as bright yellow).

The following stool colors may be also normal, if they result from ingested substances:

• Green stool may result from ingesting large amount of leafy vegetables, artificially-colored drinks, black licorice, iron or vitamin supplements. Other causes of green bovel movement.
• Black stool may be from blackberries, blueberries, iron in red meat, spinach, or iron supplements, or Pepto-Bismol. Other causes of black bowel movement. 
• Red stool may be from beets, artificial colors in drinks, sweets, or ice creams, red gelatin, tomato juice or soup. When not sure, blood in the stool has to be considered.
• Orange stool may be from vitamin A, antacids, artificial colors, butter-fish, carrots, sweet potatoes, kale, spinach, turnip greens, winter squash, collard greens, cilantro, fresh thyme.   

continue reading What Is Normal Bowel Movement Color?