What do we call the offense of unlawfully taking someone else's property without the intent to return it?

The offense of unlawfully taking someone else's property without the intent to return it is referred to as theft or larceny. This crime encompasses the unlawful taking and carrying away of someone else's personal property with the specific intention of permanently depriving that person of its ownership. The key element here is the lack of intent to return the property to the rightful owner, which differentiates it from other offenses such as burglary, where the act may involve unlawful entry but not necessarily taking property, or fraud, which typically involves deception for financial gain.

In the context of grand theft, while it is a type of theft that involves a specific monetary threshold, it still falls under the broader category of theft or larceny. Thus, theft/larceny is the most accurate term for the described offense, emphasizing the intent to deprive the owner of their property permanently.