This is the 15657th most frequent German word.
zehnjähriges
"Ten-year" or "ten-year-old."
Here, 'zehnjähriges' is an adjective describing the noun 'Kind', indicating the age of the child.
In meiner Nachbarschaft lebt ein zehnjähriges Kind.
In my neighborhood lives a ten-year-old child.
In this sentence, 'zehnjähriges' serves as an adjective indicating the duration of the anniversary.
Das zehnjähriges Jubiläum der Firma wird groß gefeiert.
The ten-year anniversary of the company will be celebrated grandly.
Here, 'zehnjährigen' (inflected form of 'zehnjähriges') describes the noun 'Freunden', indicating their age.