Fretfulness is the state of being worried, a little complaining, and unable to relax. It names the mood, not one single action: the sighing, the small complaints, the mind that will not sit down. Parents talk about a baby's fretfulness when the child is tired or unwell and cannot be soothed. In grown-up writing it can describe a tense, restless stretch of waiting. It is a fairly formal, story-like noun; in ordinary talk people are more likely to say someone is restless, anxious, or in a bad mood. It is not a medical word, though it can sit next to real discomfort.