Formal Agent: -에 의해 (By, Through The Agency Of)

This pattern connects a noun to a passive verb. It tells us who or what performed the action. In a standard active sentence, the subject does the work. In a passive sentence with 에 의해, the focus shifts. The focus is now on the result or the object. The 'agent' (the doer) is marked by this specific particle. It can also show the means or the cause of a situation. For example, a law created 'by' a government uses this. A building destroyed 'by' a storm also uses this. It behaves like a bridge between the cause and the effect. You will often see it as 에 의해서 as well. Both versions mean exactly the same thing in formal contexts. Think of the 서 as a tiny bit of extra formal flair.

1. 1Using this grammar is surprisingly simple and consistent. There are no tricky conjugations or irregular forms to memorize here. Just follow these two steps:
2. 2Take any noun or noun phrase you want to emphasize.
3. 3Add 에 의해 or 에 의해서 directly to the end of it.
4. 4It does not matter if the noun ends in a vowel or a consonant. For example, 정부 (government) becomes 정부에 의해. The word 태풍 (typhoon) becomes 태풍에 의해. Unlike many other Korean particles, there is no 'patchim' (final consonant) rule here. It is like a 'one-size-fits-all' suit for your nouns. This simplicity is a relief for anyone tired of irregular verb endings! Just remember that this pattern almost always pairs with a passive verb. Look for verbs ending in ~되다, ~어지다, or other passive forms.

This grammar is your best friend in professional settings. Use it when writing an official report at work. It is perfect for describing scientific discoveries or historical facts. You will see it constantly in news headlines and legal documents. If you are writing a university essay, this is a must-have. It is also used when the cause is an impersonal force. Natural disasters, economic trends, and social changes often use 에 의해. It gives your sentences a sense of authority and objectivity. Use it when the 'who' is less important than the 'what happened'. If you are in a job interview, it can show sophistication. Just be careful not to overdo it in spoken conversation.

Never use this with your friends or family members. If you say 'This bread was eaten by me' using 에 의해, people will laugh. It sounds like you are reading a police report about your breakfast. Avoid using it in casual texts or daily spoken Korean. In those cases, use 한테 or 에게 for people. For general causes, 때문에 is much more natural and friendly. Also, do not use it with active verbs like 먹다 (to eat) or 가다 (to go). It is strictly for passive constructions or showing a formal cause. Using it in the wrong place is like wearing a ball gown to the gym. It is technically a 'dress', but it definitely doesn't fit the vibe!

Many learners try to use it with active voice sentences. You cannot say 'I ate bread by this grammar.' Another mistake is forgetting the formal tone of the rest of the sentence. If you use 에 의해, you should use formal endings like ~습니다. Mixing this high-level particle with casual ~어/아 endings sounds very strange. It is like wearing a silk tie with pajama pants. Another common error is using it for simple human agents in casual talk. Don't use it for your mom, your dog, or your roommate. Stick to inanimate objects, organizations, or very famous historical figures. Finally, don't confuse it with ~에 의하면. That one means 'according to' and serves a different purpose entirely.

Let's compare 에 의해 with its cousins. First, we have 에게 and 한테. These also mean 'by' in passive sentences, but they are for people. They feel much softer and more natural in daily life. Second, we have 때문에. This shows cause but is way more common in speech. If a storm broke a window, 태풍 때문에 is conversational. 태풍에 의해 is what you would hear on the evening news. Think of 에 의해 as a formal 'due to the agency of'. Think of 때문에 as a simple 'because of'. Lastly, compare it to (으)로. While (으)로 shows a tool or method, 에 의해 shows the responsible party. It is a subtle difference, but important for sounding like a pro.