na-adjective, noun which may take the genitive case particle 'no'
Formal/literary adjective used to describe deep respect, gratitude, consideration, or reflection. Often appears in set phrases like 深甚なる感謝 (profound gratitude) or 深甚の意を表する (express one's deep respect).
深甚なる感謝の意を表します。
I express my profound gratitude.
深甚の注意を払って検討した。
We examined it with the utmost care.