What is the difference between 에 & 애 ?
The word 태양 uses 애.
The word 에밀리 uses 에.
But they are both pronounced the same ( 애 & 에 )
I don't get how you know when to use which.

Question

What is the difference between 에 & 애 ?
The word 태양 uses 애. 
The word 에밀리 uses 에. 
But they are both pronounced the same ( 애 & 에 ) 
I don't get how you know when to use which.

Answer

"애" is a noun meaning "a kid" or "love(愛)" while "에" is similar to a preposition like "to", "on", "in" or "at" in English. 
"태양애" doesn't make sense, it should be "태양에 (대한)"

As to "에",
에밀리에게 = To 에밀리
은행에 가다 = to go to the bank
탁자위에 있다 = It's on the table.
나는 2000년에 태어났다 = I was born in 2000
나는 언제나 6시에 일어난다 = I get up at 6 am.

As for "애",
나는 애가 둘 있다 = I have got two kids.
(here, "애" is short for "아이- kid")

애국심(愛國心) = the love of your country
(愛-love, 國- a country, 心-feeling)
애인(愛人) =  a person who you have got a romantic relationship with like bf or gf.
(愛- love, 人-a person)

\^o^/

Answer

Pascal's answer is great.
I am just answering about its pronounciation.

에 of 에밀리(Emily) sounds 'E' as in 'End'
애 of 태양(Taeyang) sounds 'A' as in 'And' even though we write it 'AE' for convenience.

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