The adjective form of the word 'Child' is -

• The adjective form of the word 'Child' is - Childlike and Childless. (ক + গ)

• Child (noun)
English Meaning: a young person especially between infancy and puberty.
Bangla Meaning: অজাত বা নবজাত মানবশিশু; বালক বা বালিকা।

Other forms:
- Childlike (adjective) - শিশুসুলভ।
- Childless (adjective) - নিঃসন্তান।
- Childlessness (noun) - নি:সন্তানতা।

Source: 
1. merriam-webster.
2. Accessible Dictionary by Bangla Academy.