The essence of synthesis can be understood in different contexts based on the provided search results. Here's a synthesis of the information:

Chemical Synthesis: In the context of chemical synthesis, the essence of synthesis refers to the process of combining different chemical compounds or elements to create something new. This can involve reactions, such as the synthesis of esters like ethyl methanoate (rum essence) through the reaction of ethanol and methanoic acid.

Total Synthesis: Total synthesis, particularly in the field of organic chemistry, refers to the complete synthesis of complex natural products from simple starting materials. It has been a flagship of chemical synthesis and a principal focus of research

Frailty and Essence: In the context of frailty, the essence of frailty refers to the core components or building blocks that define the concept of frailty. Qualitative synthesis and systematic reviews have identified commonalities and core components that together define frailty

Video Game Synthesis: In the context of video games like Atelier Ryza 2, the essence of synthesis refers to the use of essences or elements during the synthesis of items in the game.

Conceptual Essence: In a broader sense, the essence of synthesis can be understood as the act of combining or creating something new by bringing together different elements, ideas, or components

It's important to note that the essence of synthesis can vary depending on the specific context in which it is used. The examples provided above highlight some of the different meanings associated with the term.