To overcome an opponent in competition or fight
When to use
sports victory, winning a game, convincing opponent in debate
The nuance
Use 이기다 when you win against someone; it requires an opponent and indicates a positive outcome.
이기다 (i-gi-da, igida) · 지다 (ji-da, jida)
이기다 and 지다 clearly distinguish the winner and loser in a competition or game.

One lane per word — no nested boxes, just the gist.
To overcome an opponent in competition or fight
When to use
sports victory, winning a game, convincing opponent in debate
The nuance
Use 이기다 when you win against someone; it requires an opponent and indicates a positive outcome.
To be defeated by an opponent in competition or fight
When to use
sports defeat, losing a game, being convinced in debate
The nuance
Use 지다 when you lose to someone; it requires an opponent and indicates a negative outcome.
우리 팀이 축구 경기에서 이겼다.
u-ri tim-i chuk-gu gyeong-gi-e-seo i-gyeoss-da., u ri tim i chuk gu gyeong gi e seo i gyeoss da.
이기다 is used correctly to indicate winning a match.
내가 그 게임에서 졌어.
nae-ga geu ge-im-e-seo jyeoss-eo., nae ga geu ge im e seo jyeoss eo.
지다 is correctly used to express losing a game.
나는 친구를 이겼다 토론에서.
na-neun chin-gu-reul i-gyeoss-da to-ron-e-seo., na neun chin gu reul i gyeoss da to ron e seo.
Using 이기다 to indicate winning a debate is correct.
그는 시험에서 이겼다.
geu-neun si-heom-e-seo i-gyeoss-da., geu neun si heom e seo i gyeoss da.
시험 is not a direct competition against someone, so 이기다 is incorrect here.
나는 그에게 졌다 농구 경기에서.
na-neun geu-e-ge jyeoss-da nong-gu gyeong-gi-e-seo., na neun geu e ge jyeoss da nong gu gyeong gi e seo.
지다 correctly indicates losing in basketball.
나는 그에게 졌다 시험에서.
na-neun geu-e-ge jyeoss-da si-heom-e-seo., na neun geu e ge jyeoss da si heom e seo.
시험 is not a direct competition, so 지다 is incorrect.
우리 팀이 게임에서 졌다.
u-ri tim-i ge-im-e-seo jyeoss-da., u ri tim i ge im e seo jyeoss da.
지다 is correctly used for losing a game.
내가 친구를 졌다 토론에서.
nae-ga chin-gu-reul jyeoss-da to-ron-e-seo., nae ga chin gu reul jyeoss da to ron e seo.
지다 correctly expresses losing in a debate.
Which word should you use to describe the team that won a soccer match?
If you lost a game against a friend, which word should you use?
Can you use '이기다' when you get a good score on a test?