An active verb meaning to use something or to write
When to use
Using tools, Writing text, Using language, Expressing feelings
The nuance
Used when the subject actively uses a tool, language, writing, etc.
쓰다 (sseu-da, sseuda) · 써지다 (sseo-ji-da, sseojida)
'쓰다' is active meaning 'to use' or 'to write,' while '써지다' is the passive form meaning 'to be written' or 'to be used' naturally or unintentionally.

One lane per word — no nested boxes, just the gist.
An active verb meaning to use something or to write
When to use
Using tools, Writing text, Using language, Expressing feelings
The nuance
Used when the subject actively uses a tool, language, writing, etc.
A passive verb meaning something is naturally or unintentionally written or used
When to use
Passive expression, Natural occurrence, Action by others
The nuance
Used when the subject does not act directly but something is written or used passively or naturally by others or circumstances.
나는 편지를 쓴다.
na-neun pyeon-ji-reul sseun-da., na neun pyeon ji reul sseun da.
The subject actively writes a letter, so '쓴다' is correct.
편지가 써진다.
pyeon-ji-ga sseo-jin-da., pyeon ji ga sseo jin da.
Indicates the letter is being written by someone or naturally, so '써진다' is correct.
나는 이 펜을 써진다.
na-neun i pen-eul sseo-jin-da., na neun i pen eul sseo jin da.
'Pen' is actively used, so '쓴다' should be used. '써진다' is passive and inappropriate here.
이 글은 내가 쓴다.
i geul-eun nae-ga sseun-da., i geul eun nae ga sseun da.
The subject actively writes the text, so '쓴다' is correct.
이 글은 내가 써진다.
i geul-eun nae-ga sseo-jin-da., i geul eun nae ga sseo jin da.
Subject is the doer, so passive '써진다' is incorrect; '쓴다' is correct.
이 단어는 자주 쓰인다.
i dan-eo-neun ja-ju sseu-in-da., i dan eo neun ja ju sseu in da.
The word is frequently used passively, so '쓰인다' is correct.
이 단어는 자주 써진다.
i dan-eo-neun ja-ju sseo-jin-da., i dan eo neun ja ju sseo jin da.
'써지다' fits naturally written sentences; for word usage frequency, '쓰이다' is correct.
나는 감정을 쓰다.
na-neun gam-jeong-eul sseu-da., na neun gam jeong eul sseu da.
Expressing feelings actively, so '쓰다' is correct.
Choose the correct word: 'This letter is ___ by someone.'
Which sentence shows active usage?
Which word fits: 'This word is often ___.'
What does it mean?