as a noun, 'major' can refer to a military rank or an academic specialization.
in the context of academia, it refers to one's primary field of study. In a military context, it refers to a rank above captain and below lieutenant colonel.
Her major in college was biology.
The major gave the orders to his troops.
Choosing a major can be a challenging decision for many students.
remember that 'major' in an academic context doesn't always mean it's the most important; it's just the primary focus of study.
as an adjective, 'major' describes something of greater importance, seriousness, or significance.
it can be used to describe events, decisions, incidents, subjects, etc., that have a significant impact or role.
The company faced a major setback this quarter.
Climate change is a major concern for many scientists.
She played a major role in the project's success.
don't confuse 'major' with 'majored.' The latter refers to specializing in a particular academic subject.
as a verb, 'major' means to pursue an academic subject as one's primary field of study.
She decided to major in psychology.
Many students at that college major in engineering.
I'm not sure what I want to major in yet.
the verb 'major' is specific to academic contexts. Don't use it in non-academic settings expecting the same meaning.