This is the 539th most frequent Japanese word.
来年
"Next year."
The word '来年' (raien) is a noun meaning 'next year'. It is used here to specify the time when the action of visiting Japan will take place.
来年、私は日本を訪れます。
Next year, I will visit Japan.
'来年' (next year) is used here as the time frame for the summer ('来年の夏', 'next year's summer') being discussed.
来年の夏はとても暑くなると言われています。
It is said that next summer will be very hot.
'来年' is used to specify the desired time frame (next year) for the action of traveling with friends, showing a conditional or hopeful statement.