A three letter word starting with the letter D can carry many meanings. For example, DAD is a term of endearment for fathers and has multiple variations such as papa, papi, daddy and dada. The word DAY is typically used to refer to a 24-hour period in which sunlight is present. Additionally, the word DEN functionally serves as an animal’s shelter or refuge from predators. It also refers to an enclosed place where a person may feel safe or protected. Other notable words include dot, dry, dug and dye.