auxiliary
Attaches to the dictionary form of a verb to express obligation, expectation, or strong recommendation. In modern Japanese, べき is often followed by だ/です or directly modifies a noun.
You should study more.
You should study more.
He ought to apologize right away.
彼の言うことを信じるべきではない。
You shouldn't believe what he says.
I should have said it sooner.
Let's think about what we should do now.
べき expresses a stronger sense of duty or obligation, while 方がいい offers softer, benefit-based advice.
べき is the standard modern equivalent of べし for expressing obligation, while べし is archaic/literary and mainly found in set phrases or classical texts.
べき expresses that something should or ought to be done based on judgment or duty, whereas でなければならない more directly states that a certain identity or condition is required.
べき expresses what one should do as a moral or logical judgment, whereas ならない (as なければならない) states a more direct, unavoidable necessity or obligation.
べき means 'should/ought to' in the affirmative, while べきではない is its negative form meaning 'should not'.
Derived from the classical auxiliary べし, which expressed obligation, expectation, or suitability. The modern form べき is the attributive form that became the base for contemporary usage.