How do you say this in Korean? (You)

See a translation

Many study books say English 'you' is '당신' in Korean.
But this is a big mistake.
I do not think this big mistake is due to editor's carelessness.
This mistake is due to Korean language's character.
English 'you' covers almost all cases, but there is no word exactly equivalent to English 'you' in Korean.
너 is close to 'you' but 너 can be used to friends or familiar younger people than the speaker. 너 is informal or casual.
There is no word equivalent to 'you' which can be used to older people or higher ranker than the speaker.
Koreans use hearer's position, not 당신 to imply 'you' when the speaker says to older people or higher ranker, or unfamiliar younger people.

Ex)
Are you tired, dad/mom? => 아빠/엄마 피곤하세요? wanting to use informal : 아빠/엄마 피곤해?
There is no saying 'you' (in Korean), is just position 아빠. (There is no saying 당신.)
The Korean language has many words to imply 'you' (in Korean) instead of '당신' (but i'll write a lot): 선생님(teacher), 사장님(head of company), 어르신(honorific word refers to older person, used by younger person), 이모(aunt, used by younger person), 언니(younger sister calling older sister), 오빠(younger sister calling older), 형(younger brother callingt 학생(student), 젊은이(young adult/person), 기사(taxi/bus driver)님(sir/mr/mrs), 고객님(customer, department stores or customer counseling offices) / 손님(guest/visitor), 의사 / 선생님 or 의사 + 선생님 = 의사선생님(doctor), 사모님(madam), 할머니(grandmother), 할아버지(grandfather)

when to use "당신"? : http://www.yousuckatkorean.com/2011/06/using-%E...

(From Astrophil's answer):

We(They) usually add 씨 after his/her name and/or 님 after a position.

Maria => 마리아씨 Or 마리아님
Bongwoo => 봉우씨 Or 봉우님

To a teacher: 선생님
To a professor: 교수님
http://koreanwikiproject.com/wiki/index.php?tit... if you are in korean company. Read from "Positions (직책)"

And we(they) usually say 선생님 to a stranger who looks older than the speaker. It doesn't have to do with "a teacher" and don't have any other particular to name to call them.

그대 is like, an old and (very) formal word, not used in life. It has been used in a poem, lyrics... etc(당신 is also used in lyrics)
별에서 온 그대
(You who came from the star, a title of kdrama).
my love = 내 사랑

자네 is used when older person calls younger person "자네". 자네 is 하게체 = familiar style.

그쪽 means you, literally means that side, younger person calling strangers/older person