What is define should?

"Should" is a modal verb used to convey a sense of obligation or duty with regard to an action or event. It is often used to offer advice, make suggestions, or give recommendations. The word "should" is also commonly used as a marker of conditional statements, indicating what would be expected or required in a particular situation. In many contexts, the word "should" is used to express a sense of moral or ethical duty, as in "I should apologize for my behavior" or "You should always treat others with respect." However, the use of "should" can also be subjective and dependent on personal beliefs or cultural norms.