"Just" with だけ, のみ, ばかり, and しか

だけ, のみ, and ばかり are variations of "just" or "only". しか is similar, but it can only be used in negative statements.

だけ means "just so", in terms of amount. It acts like a particle.

俺だけ行く
Only I will go

俺だけじゃないよ
It's not only me.

のみ is like a less colloquial だけ.

味付けは塩コショウのみ。
There is only salt&pepper as flavoring

ばかり is yet another "only" word. It can also be pronounced ばっか or ばっかり. Xばかり focuses on everything falling within the definition of X as being true, whereas だけ and のみ focus on things that fall outside of the statement being false. Think of the difference in vibes between "There is only this" and "There is nothing else".

悪いことばかりじゃないと思います。
I don’t think it’s all bad things.

分からないことばかりだった
It was all stuff I didn’t understand.

The structure <verb>てばかりいる is often used to convey a critical attitude towards someone stating they do just one thing over and over to the point where it’s detrimental.

彼は寝てばかりいる
He does nothing but sleep

ばかり can also be used with temporal statements to convey how soon or early something happened.

戦いはまだ始まったばかりだ。
The battle has only just started.

しか is used with negative statements to convey the same meaning as だけ but with the focus on everything else that is not what is being marked.

僕しかいない
There is no one else other than me here

The compound だけしか exists too. It works exactly the same as しか but has stronger emphasis.