Infancy/ˈɪnfənsi/ Definition 1 of 2Pro Tip 1/3Growth Stages Refers to early human stages, preceding toddler age; not used for older children. Her motor skills were impressive even in infancy. Pro Tip 2/3Parental Bonding Often involves discussion on parental care or child development themes. Attachment between mother and child can form during infancy. Pro Tip 3/3Developmental Phases Used in the context of milestones or health, such as walking and talking. Babies usually begin speaking simple words in late infancy.