noun
importance; seriousness; gravity
Abstract noun emphasizing the weight or significance of a matter, often used in formal or serious contexts.
この問題の重大性を認識しなければならない。
We must recognize the seriousness of this problem.
事
In light of the gravity of the incident, special measures were taken.
深刻さ emphasizes depth of seriousness or severity, often with a negative or worrying connotation, whereas 重大性 is more neutral and objective.
Compound of 重大 (じゅうだい, 'serious, important') + suffix 性 (せい, '-ness, -ity'), forming an abstract noun.