What's the difference between 우(佑) and 좌(佐)?

ANSWER: Both mean help, but 우 (佑) seems to refer to help from above while 좌 (佐) seems to refer to help from below.

The Chinese character 右 (우) means right or right hand, and the Chinese character 左 (좌) means left or left hand. And the character 人 (인) or 亻(인) means person. While 人 is normally used by itself, the character 亻(인) is used only as a component of composite characters, such as in the characters 佑 (우) and 佐 (좌). Therefore, the components of 佑 and 佐 literally translate as "a person's (亻) right hand (右)" and "a person's (亻) left hand (左)."

The phrase 천우신조 (天佑神助) can translate as divine care or grace of God, so the phrase 천우신조로 translates as by the grace of God, but the phrase 천우신조 (天佑神助) literally translates as "Heaven's (天) help (佑) [and/or] God's (神) help (助)." When referring to help from Heaven, notice that 우 (佑) was used, not 좌 (佐)

The first sentence of Korea's national anthem reads as follows:

동해(東海)물과 백두산(白頭山)이 마르고 닳도록 하느님이 보우(保佑)하사 우리 나라 만세(萬歲).

Until the waters of the East Sea (동해물) dry up (마르고) and Mount Baekdu (백두산) wears away (닳도록), God (하느님이) protect (보 保) and help (우 佑) our country (우리 나라) ten thousand years (만세).

Notice that the subject 하느님 (God) was used with the verb 보우(保佑)하다, which means to protect (保) and help (佑). Again, when the subject is God, the character 佑 (우) is used, not 佐 (좌). In addition, the character 우 (佑) or the verb 보우(保佑)하다 seems to have been used to refer not only to help from God but also to help from kings and emperors. This is why I wrote that 佑 (우) seems to refer to help from above.

As for the character 佐 (좌), it is used in the verb 보좌(保佐)하다, which also means to protect (保) and help (佐), but it refers to giving protection and help to a superior. 보좌관 (補佐官), for example, translates as an aide, and 보좌인 (保佐人) as an assistant, a counselor, or an advisor, suggesting that the character 佐 (좌) is used when referring to help from below.

In summary, one seems to get help (우 佑) from God and king but gives help (좌 佐) to one's king or superiors. In other words, help from a person's right hand (佑), and help to a person's left hand (佐).