Assault in Utah is attempting to do injure to another person, making a threat to another person and immediately showing that you can back up your threat (usually showing a weapon),  or actually injuring  another person.  This statute is broad so that it can encompass almost anytime a person tries to injure another person.  Simple assault is a Class B misdemeanor.  It can become a Class A Misdemeanor if the victim is actually injured or the victim is pregnant.

An simple assault becomes an aggravated assault in Utah if the person intentionally causes injury or uses a dangerous weapon.

Utah Code § 76-5-102: Assault
(1) Assault is: (a) an attempt, with unlawful force or violence, to do bodily injury to another; (b) a threat, accompanied by a show of immediate force or violence, to do bodily injury to another; or (c) an act, committed with unlawful force or violence, that causes bodily injury to another or creates a substantial risk of bodily injury to another.

Utah Code § 76-5-103: Aggravated assault
(1) A person commits aggravated assault if he commits assault as defined in Section 76-5-102 and he: (a) intentionally causes serious bodily injury to another; or (b) under circumstances not amounting to a violation of Subsection (1)(a), uses a dangerous weapon … or other means or force likely to produce death or serious bodily injury.