Definition:
unique is a descriptive adjective which suggests that something is one-of-a-kind or without an equal. It can be used to describe something that is unlike anything else, and thus highly special or particular.
Rules:
unique is used to describe a single item, or group of items, that have distinguishing characteristics setting them apart from all other items like it. Thus, it tends to be used when speaking of something that is rare, unusual, or special in some way. It can't be used to describe something merely different or particular. If two items are not one-of-a-kind, they cannot be described as unique.
Examples:
1. This hand-crafted fabric is a unique piece of artwork.
2. This restaurant's menu has some unique flavors.
3. She has a unique sense of style.
Tips:
when using unique to describe something, be sure to have sufficient evidence that the item/group of items in question is truly without an equal. Otherwise, it can be seen as a false claim or exaggeration.