Adversatives with が, けど, しかし, and ても/でも

Unrelated to the subject marker が, the conjunction が states that, even though the former statement is true, the latter statement is also true. With が, both statements are independent clauses. Often, but not always, the second statement is in contrast with the first statement. This is commonly translated as “but” or “although”, but there are cases where it’s simply just an “and” and there is no contrast at all.

少し早いですが、おめでとうございます。
It is a bit early but, congratulations

が attaches after a complete sentence, meaning after nouns and な adjectives it requires だ (or です). ですが is common in speech and everyday polite language, but だが sounds too stiff and it’s almost exclusively left to written or very formal language.

Same as が, there is also the conjunction けど. Their usage and meaning can be considered pretty much the same. Just like with が, both ですけど and だけど exist and are very common in conversational tone in real life too. けど comes across as less formal than が. 

しばらく考えてみたけど、何も思い浮かばなかった。
I tried thinking about it for a bit but I couldn’t come up with anything.

けど and が both cover a formality/politeness space that can feel very nuanced, so here’s a few rules of thumb. These aren’t actual rules, just general advice:

  • If the entire sentence is in plain form, use (だ)けど
  • If it’s conversational language, don’t use (だ)が
  • If the entire sentence is in polite form, use ですが
  • Ending a statement with polite form but using けど in the middle is common, but can come across as unnatural if the politeness level isn’t appropriate

A very common usage of が/けど is to introduce something as a topic in an indirect manner. In this usage it does not have a nuance of adversative (“but”). It is simply introducing something before talking about it. It is common to see this usage with the explanatory の particle like なんだけど or なんですが:

「もしもし、ネミアちゃん？　俺だけど、どうしたの？」
(on the phone) “Hello, Nemia? It’s me, what happened?”

This usage is very common when easing the listener into a request or question you have for them:

一つお願いがあるんですが、よろしいでしょうか？
I have one request... would that be okay?

This type of phrase is so common that in many situations the speaker doesn’t even need to provide an explanation after the んですが/んだけど, to the point where the second half of the sentence can be completely dropped.

すいません、本を探しているんですが
(In a store) I’m sorry, I’m looking for a book... (could you help me?)

けど can also show up as けれど and けれども. They are mostly the same, but the longer it is, the more formal it sounds.

しかし is an interjection. It sounds formal. English speakers tend to overuse this because it resembles how we use “but” at the beginning of sentences in our language but in Japanese it is not that common.

しかし、知らなかった。
However, I did not know.

ても is a combination of the て form and も. It works as a conjunction stating that the statement after it is true despite the statement before it. This is like an adversative, but it's not always one.

そんな事言わなくてもわかっているんだろ？
Even if I don't tell you that, you understand right?

There is also でも that can be used to add an adversative "but" meaning at the beginning of a new sentence.

でも、あなたは分かっているでしょ？
But you get that, don't you?