Function $f$ subordinate to function $g$

147 Views Asked by At

I'm trying to study a research paper, during that i come across this word Subordinate, i searched this a lot on google but didn't get any satisfactory answer. I understand the definition they gave in this paper, but the problem is what they want to convey and what is the purpose of this, how will this help. Please help me with this

Here i a screenshot

enter image description here

Thankyou