This is the 214th most frequent Korean word.
씨
A suffix in Korean used as a polite term of address, similar to "Mr.," "Ms.," or "Mrs." in English.
Here, '씨' is used as a respectful title after a surname (김), equivalent to 'Mr.' or 'Ms.' in English.
김 씨가 편지를 보냈습니다.
Mr. Kim sent a letter.
Here, '씨' refers to 'seeds,' which is a homonym in Korean with a completely different meaning from the usage as a respectful title.
씨는 식물이 자라나는 데 중요한 것입니다.
Seeds are important for plants to grow.
Here, '씨' is part of a compound word '씨앗,' which means 'seed' and is used metaphorically to describe the origin of something negative.