What is the name of the process that converts the elemental form of nitrogen to simpler forms, making it available for use by living organisms?

The process that converts the elemental form of nitrogen to simpler forms so that it can be used by living organisms is called nitrogen fixation. This process is essential for the nitrogen cycle, which involves the movement of nitrogen between the atmosphere, soil, and living organisms. Nitrogen fixation is carried out by certain bacteria, such as Rhizobium, which convert atmospheric nitrogen into a form that plants can use. This process is vital for the growth and development of plants and ultimately affects the entire ecosystem. 

Canning and phosphorus fixation are unrelated processes that do not involve the conversion of elemental nitrogen to simpler forms.