The crime of assault varies from state to state (and under federal law), but is generally defined as intentionally putting another person in reasonable apprehension or fear of an imminent (immediate) harmful or offensive contact. The crime of assault may be committed even if there is no physical contact, as the criminal physical contact constitutes the separate crime of battery.

The crime of assault with a deadly weapon (also known as aggravated assault) occurs when someone uses a deadly weapon (gun, knife, club, tire iron, brass knuckles, etc.) during an assault.

In Missouri, assault is codified under Missouri Revised Statutes, Chapter 565. Assault offenses are categorized into different degrees, with varying levels of severity and punishment. Simple assault, which might involve causing another person to fear immediate bodily harm, is generally considered a misdemeanor. However, the crime escalates to a felony when it involves special victims, serious physical injury, or is committed with a deadly weapon or dangerous instrument. Specifically, assault with a deadly weapon, known as 'armed criminal action' or 'aggravated assault' in Missouri, is a more serious offense and typically constitutes a felony. This type of assault implies that the perpetrator has acted with the intent to cause serious physical injury or death, or has acted recklessly with extreme disregard for the value of human life. The exact charges and penalties depend on the circumstances of the case, including the degree of injury, the intent of the perpetrator, and the use of a weapon. Penalties for aggravated assault can include significant prison time and fines.