Bad is a word used to describe undesirable circumstances, objects, or events.

Though bad often is used to imply moral turpitude of a person, the term more specifically refers to an unfortunate circumstance. While bad is often used as a synonym for evil, bad can also refer to something flawed or unusable. In works such as On the Genealogy of Morals, the philosopher Friedrich Nietzsche made much of a distinction he drew in German between the böse, ("evil"), which he was prepared to admire, and the schlecht ("bad"), which he disdained; in Nietzsche's thought, evil was powerful, menacing, and dangerous; bad was weak and ineffective. In African-American vernacular English, and varieties of American English that have been influenced by it, bad or badass are frequently used as compliments, an example of rhetorical irony. "Badass" can also be used to describe a person prone to physical altercations.

Amusingly for English speakers, in Germany Bad (German for "bath") is a prefix for town names signifying a spa town, as in Bad Wörishofen or Bad Kissingen. When a person is bad (look up the term ruthlessness) it causes for that person to behave rudely and crimefully.

Bad as the opposite of good is an ideal. Evil is a type of bad, and therefore is not one unless considered as the opposite of good. Absolutes such as bad and good are like a perfect ten. They are unattainable, because there is always something better or worse, respectfully. When we say that something is either bad or good, we mean that it is mostly bad or mostly good.

Core issues in ethics

• in African-American Vernacular English, the term "my bad" is used frequently in place of "my fault"

Bad