What is the name of the biological process that converts atmospheric nitrogen into a form that can be used by plants?

Nitrogen fixation is a process carried out by certain types of bacteria, such as Rhizobium, which live in the soil and form a symbiotic relationship with plants. 

During nitrogen fixation, atmospheric nitrogen (N₂) is converted into a more chemically reactive form, such as ammonia (NH₃), which can then be further converted into nitrates (NO₃^-) that can be easily absorbed by plants as a source of nitrogen. This process is crucial for the growth and development of many plants, as nitrogen is a critical component of proteins and nucleic acids like DNA.