ACR Appropriateness Criteria® Patient Age Definitions

Definition of terms used to describe patient age information in the ACR Appropriateness Criteria® topics.

Neonate – Birth to 28 days old1.

Infant – Birth to one year old2.

Child – Younger than 18 years old3.

Adolescent – A transitional stage of physical development occurring between puberty and adulthood4

Adult –18 years old or greater.

Pregnancy age - Menarche to menopause (generally in the range of 10-60 years old).


1Merriam-Webster Dictionary. Accessed 21 March 2011.

2World Population Prospects: The 2019 Revision of World Population Prospects. Available at: Accessed October 20, 2021.

3Convention on the Rights of the Child. UNICEF publications. Available at: Accessed 21 March 2011.

4Christie D, Viner R. Adolescent development. BMJ 2005;330:301-4.