What is the major source of nitrogen in our atmosphere?

The major source of nitrogen in our atmosphere is molecular nitrogen (N₂), which makes up about 78% of the Earth's atmosphere by volume. This nitrogen is largely inert and does not readily react with other substances, which is why it remains abundant. Nitrogen is essential for life, as it is a key component of amino acids and nucleic acids, but it must be converted into reactive forms by processes such as nitrogen fixation for biological use.