Is there a difference between pagerank and page rank?

Many people think that pagerank and page rank are the same thing, others think that pagerank is just page rank with some spelling error.

In fact, pagerank and page rank are completely different.

Pagerank is a Google trade mark and it is a measurement unit that Google developed to measure the importance and value of a webpage based on many factors like the inbound links, anchor text, and others, for more information about pagerank click here.

but page rank is about how webpage ranked or positioned in search engine for a given keyword.