Commonwealth Day

5.4

An annual day when Commonwealth countries celebrate their unity and shared values

proper noun

: Día de la Commonwealth

Schools across the United Kingdom hold special assemblies to mark Commonwealth Day every March.

Examples

Commonwealth Day is an opportunity to reflect on the shared values of the member countries.
On Commonwealth Day, the Queen delivers a message to all the nations in the Commonwealth.
Today is Commonwealth Day!
Many schools celebrate Commonwealth Day with special events.
Commonwealth Day is an opportunity to reflect on the shared values of the member countries.
On Commonwealth Day, the Queen delivers a message to all the nations in the Commonwealth.
Schools across the United Kingdom hold special assemblies to mark Commonwealth Day every March.

Surface Forms

Commonwealth Day main

Morphology

commonwealth + day

The meaning is directly derivable from combining 'commonwealth' (an organization of independent countries with shared ties) and 'day' (a calendar day set aside for an event): it names a day associated with the Commonwealth. This follows the common '[entity] Day' compositional pattern (e.g., Independence Day), so a B1 learner who knows both constituents would reasonably infer the MWE's meaning.

Etymology

Commonwealth Day gets its name from Commonwealth, which once meant the 'common good' shared by a group of countries. It began as a day to mark Queen Victoria's birthday, so today it is a time when member nations come together to celebrate their 'shared values' and unity.