The particle -만 is a simple, but a useful one to know. You use it to indicate that something is the only thing to the exclusion of everything else. Pretty simple. Though there are some that confuse it with another highly similar Korean particle.
As mentioned, the particle -만 is a particle that indicates that the word it is attached to is the only thing/option to the exclusion of everything else. Furthermore, when you use it with a number it can also indicate a minimum that is required.
This does remind a lot of people of the particle -밖에, which has on first glance a similar meaning. However, they are not the same. Whereas, -밖에 is an inherently negative particle (implying dissatisfaction or other negative emotions), -만, on the other hand, does not carry such emotional load.
가: 지금 공항에 출발해야 해요!
나: 알겠어요. 오 분만 기다려 주세요.
A: We have to leave for the airport now!
B: Okay. Please wait for just five minutes.
How To Use
The particle -만 is a rather easy particle to use as it follows the very simple ‘no rule’ grammar rule. This means you simply attach it to the noun without worry about consonants or vowels. After attaching it, you are pretty much done.
The particle -만 can be used and is often used with other particles. Although there are a few rules you have to keep in mind to ensure you make no mistakes. The particle -만 can replace the particles -은/는, -이/가 or -을/를. Or, you can use them together with -만 being written first. This forms -만은, -만이 and -만을 respectively. However, you cannot replace all other particles, like -에서, -에게, -까지, with -만, so you will have to use them together. With them, you write -만 at the end. A few examples, -에서만, -에게만, -까지만.