rātrim

 The word "rātrim" in Sanskrit is written as 

"रात्रिम्" and is the accusative singular form 

of "रात्रि" (rātri), meaning "night."

Explanation:

• The noun रात्रि (rātri) is feminine and means "night."
• Sanskrit nouns take different forms depending on case 
• (vibhakti) and number (singular, dual, plural).
• In this context, "rātrim" (रात्रिम्) is the accusative singular 
• (object case) and is commonly used when "night" is the 
• object of a verb.
• For reference, some other forms of रात्रि include:
  • Nominative singular (subject): रात्रि (rātri)
  • Instrumental singular (by/with night): रात्र्या (rātryā)
  • Genitive singular (of night): रात्र्याः (rātryāḥ)
  • Dative singular (for/to night): रात्रये (rātrye)
  • Plural nominative: रात्रयः (rātrayaḥ)

Thus, "rātrim" is the proper Sanskrit rendering in the accusative 

singular form, suitable for poetic or classical usage.

If you want, I can also provide a full declension table of रात्रि in 

Sanskrit for all cases and numbers to give a complete view 

of its usage.