Two different ways to say 'year' in Korean : 해(hae) 년(nyeon)

해(hae) and 년(nyeon) both stands 'year'.

While 해(hae) is original Korean, 년(nyeon) is sino-Korean word (Chinese originated) - 年. Therefore, 해(hae) is used with original Korean words and 년(nyeon) is used with sino-Korean words.

Examples

□ this year: 올해 ol-hae
□ new year: 새해 sae-hae
□ They were born in the same year.
- 그들은 같은 해에 태어났다. 
- geudeureun gateun hae-e tae-eonatta.
□ for two years: 이 년 동안 yi nyeon dong-ahn
□ year 2018 2018년 (이천 십 팔 년) yicheon shib pahl nyeon
□ I bought a house last year.
- 나는 작년에 집을 샀다. 
- naneun jakneyone jibeul satta.

I know it is not easy to know the word is original Korean or sino-Korean. So it's better to learn the set expressions(such as 올해, 작년, 내년...)