Final answer:
Developmental assessment is an evaluation process, developmental delay refers to falling behind on developmental milestones, which represent key skills and abilities typically achieved by certain ages.
Step-by-step explanation:
A developmental assessment is an evaluation of a child's physical, cognitive, and psychosocial growth to ensure they are developing at a typical rate compared to same-age peers. In contrast, a developmental delay is when a child does not reach developmental milestones at the expected times. Developmental milestones are the specific normative events and abilities that most children achieve by certain ages, such as crawling, walking, speaking in sentences, etc. If multiple delays in milestones are observed, it may indicate a need for early intervention, which is why tracking these milestones is essential for a child's development.
For example, holding up the head is a developmental milestone usually reached at around 6 weeks of age. If a child cannot hold their head up by 4 months, this would be considered a delay. Infancy and early childhood are critical periods where rapid growth and skill accumulation occur, so differences in development are most noticeable.