What constitutes 'theft' legally?

The concept of theft, as defined legally, involves the unlawful taking of someone else's property with the intent to permanently deprive the owner of it. This highlights two crucial elements of theft: it must be unlawful, meaning that the property is taken without the consent of the owner, and there must be a specific intent to not only take the property but to ensure that it is not returned.

In contrast, simply intending to borrow someone else's property, without the intention of permanently depriving the owner, does not meet the necessary criteria for theft. Similarly, if the property is taken with the intent to return it, this indicates a different intention and therefore cannot be classified as theft.

The unauthorized use of someone else's property without the intent to deprive also fails to qualify as theft, as it lacks that critical intention to permanently deprive the owner of their property. Thus, option C correctly encapsulates the legal definition of theft by emphasizing both the unlawful act and the clear intent to permanently deprive the owner of their property.