This is the 407th most frequent Chinese word.
主
"Master," "host," or "main."
Here, "主" is used as an adjective to mean 'main' or 'primary', describing the subjects.
主课内容是数学和物理。
The main subjects are mathematics and physics.
In this example, "主" is part of an expression, indicating respect to someone's decision or intent.
请主您的意愿行事。
Please act according to your wishes.
In this sentence, "主" is used as a noun meaning 'chief' or 'leader'.