principal

principal adjective [ always before noun ] uk/ˈprɪnsəpəl/ us
B1 main, or most important

главный, основной
Her principal reason for moving is to be nearer her mother.

PRINCIPAL noun

[ C ] uk/ˈprɪnsəpəl/ us
B2 the person in charge of a school or college

директор (школы, колледжа)
She was caught smoking and sent to see the principal .