In terms of CPR, a child is generally defined as someone who is older than one year but has not yet reached puberty. Puberty is identified by breast development in females and the presence of underarm (axillary) hair in males. This definition is significant because CPR techniques differ between infants, children, and adults based on developmental and anatomical differences.

For CPR purposes, child CPR is typically performed on those from age 1 until puberty, involving specific adjustments in compression depth, hand placement, and ventilation rates compared to adult CPR.