Colic (also known as infantile colic) is a condition in which an otherwise healthy baby cries or displays symptoms of distress (cramping, moaning, etc.) frequently and for extended periods, without any discernible reason. The condition typically appears within the first month of life and often disappears rather suddenly, before the baby is three to four months old, but can last up to 12 months of life. One study concludes that the chances of having colic is lower in breastfed babies.

The crying often increases during a specific period of the day, particularly the early evening. Symptoms may worsen soon after feeding, especially in babies that do not belch easily.^{[citation needed]}

The strict medical definition of colic is a condition of a healthy baby in which it shows periods of intense, unexplained fussing/crying lasting more than 3 hours a day, more than 3 days a week for more than 3 weeks. However, many doctors consider that definition, first described by Morris Wessel, to be overly narrow and would consider babies with sudden, severe, unexplained crying lasting less than 3 hours/day as having "colic" (so-called "non-Wessel's" colic). In reality, this extreme version of colic is more likely to be the final stage of a condition that has worsened for a few weeks.^{[citation needed]}