national anthem
Refers to the official song of a country, such as 君が代 for Japan.
The national anthem was played at the Olympic opening ceremony.
Japan's national anthem is 'Kimigayo'.
We sang the national anthem at the opening ceremony.
The athletes stood and sang the national anthem together.
The national anthem played at the ceremony hall.
国旗 is the national flag while 国歌 is the national anthem, and the two are often taught together so learners may mix them up.
校歌 is a school song sung at school events, whereas 国歌 is a country's official anthem, and the shared 歌 makes them easy to confuse.
国歌 is counted with 首 as it is a song or poem, e.g. 国歌一首.
Compound of 国 (country) and 歌 (song). The reading こっか is a regular on'yomi combination.