I learned these two words the other day from one of my adult students. She knows I'm gay and doesn't really care, but is curious and has questions. She was asking if I thought gayness was hereditary or learned behavior the other day and taught me some new Korean words.

선천적 (seon-cheon-jeok)

선천적 means nature (in the sense of innateness not trees, unicorns or butterflies). You could say something like '제 생각에는 선천적인것 같애요', which means 'I believe that people are born gay.'

후천적 (hu-cheon-jeok)

This second word refers to the other side of the debate. If something is 후천적, it is acquired through life experience. For example, '성격은 후천적으로 형성된다' means 'You can form your own personal character in the course of your lifetime.'

While I definitely lean heavily on the side that argues homosexuality is an innate characteristic (I realized I liked men in a sexual way right around puberty) I also don't think it really matters. Whether you were born gay or some experiences you had resulted in you liking members of your own sex, you should be allowed to have sex with, and love, whoever you want.
I wasn't able to communicate these thoughts with my student, but at least I have some new vocabulary words to work with. ^^