Here's why:
* "Island" is a noun: It's a thing, a place. Sentences need a subject and a verb to make a complete thought.
* Sentences need context: You need to know what you want to say about the island to create a sentence.
Examples of sentences using "island":
* "The island was covered in lush vegetation."
* "We spent our vacation on a tropical island."
* "He dreamt of escaping to a secluded island."
Tell me what you want to say about the island, and I can help you write a sentence!