This is the 16865th most frequent Russian word.
совершеннолетия
"Совершеннолетия" means "adulthood" or "majority" (the legal age of adulthood).
The word 'совершеннолетия' means 'age of majority' here, referring to the legal adulthood age.
Он достиг совершеннолетия и теперь может голосовать.
He has reached the age of majority and can now vote.
In this instance, 'совершеннолетия' refers to the occasion or process of coming of age.
Празднование совершеннолетия стало важным событием для всей семьи.
The celebration of coming of age has become an important event for the whole family.
Here, 'совершеннолетия' pertains to the specified age at which one is considered legally an adult.