Kid/kɪd/ Definition 1 of 4Pro Tip 1/3Age Range Typically refers to people from infancy to late teens. Some kids start walking as early as 9 months old. Pro Tip 2/3Colloquial Use Often used informally, even for adults, in a playful or affectionate manner. I'm meeting up with the kids from college tonight. Pro Tip 3/3Emotional Nuance Can imply tenderness or parental care when used by adults about children. I have to get home to my kids after work.