〜こそ
Precisely, the very (emphasis)machine translation
FormationNoun + こそ（replacing は／が）
こそ stands in for は or が to shine a spotlight on the preceding word: "precisely this one, not anything else." 健康こそ一番大切なものだ (health is the very thing that matters most) — implicitly compared with money or fame.
The phrase 今年こそ carries a whole story with it: previous attempts failed, and this time it absolutely must succeed — 今年こそ試験に合格したい (this year for sure, I want to pass the exam). You also meet こそ every day in the reply こちらこそ: "it's I who should (thank/apologize to) you." At a higher level there is also からこそ, emphasizing a reason ("precisely because…") — just recognize it when you meet it in reading passages.
こそ is the polar opposite of なんか・なんて: こそ lifts the preceding word up to the status of "the very one," while なんか pushes it down to "something like that." Master this opposing pair and you've covered both grammar points in one go.
Examples
今年こそ、試験に合格したいです。
This year for sure, I want to pass the exam.
「ありがとうございました。」「こちらこそ。」
"Thank you very much." "It's I who should thank you."
健康こそ一番大切なものだと思います。
I think health is the very thing that matters most.