उपसर्ग 'Upasarga (prefix) is one term used in Sanskrit grammar. "Upasarga' term results when the words like प्र, परा links with/or are used with action word (root from of a verb) like . Students of Sanskrit language know that when 'Upasarga' (prefix) is added to a root from of a verb the meaning of the root form changes. The concept of this Nyaya is based on this understanding.
Every root verb has a meaning of its own but when it is added to soem 'Upasarga'its meaning gets changed. In the same way every person has his/her own purpose /objective but when he gets associated with some other special person, as the root form of the verb gets attached to some 'Upasarga', his purpose / objective (of life) gets changed.
For example, there is a family of labourers, a child of such a family passes his whole day playing and wandering, but when he getting admitted in a school gets associated with a teacher his purpose (of life) gets changed. A root form of a verb in the form of a child getting associated with an 'Upasarga' in the form of ateacher his purpose objective changes. In the same way a diseased person getting associated with a doctor, King with his subject customer with a businessman can change and purpose objective.