किमर्थम् means why or for what.
In reply add अर्थम् to noun.
Usage:
माता किमर्थं देवालयं गच्छति? Why is mother going to the temple?
माता पूजार्थं देवालयं गच्छति| Mother is going to the temple for worshipping.
बालकः किमर्थं क्रिडाङ्गणं गच्छति? Why is the boy going to the playground?
बालकः क्रिडार्थं क्रिडाङ्गणं गच्छति| The boy is going to the playground for playing.
छात्रः किमर्थं विद्यालयं गच्छति? Why is the student going to school?
छात्रः ज्ञानार्थं विद्यालयं गच्छति| The student is going to school for knowledge.
पुरुषः किमर्थं पुस्तकं पठति? Why is the man reading the book?
पुरुषः आनन्दार्थं पु्स्तकं पठति| The man is reading the book for joy.
महिला किमर्थं गृहं गच्छति? Why is the lady going home?
महिला पचनार्थं गृहं गच्छति| The lady is going home for cooking.
युवकः किमर्थं गृहं गच्छति? Why is the youth going home?
युवकः स्नानार्थं गृहं गच्छति| The youth is going home for taking bath.
