Instructions: Generate the answer for a given question. The question requires common knowledge of English. Make sure that the answer is in detail, long, consistent with the context, and requires general knowledge of English. To be less repetitive, please vary your language for each question. Give a proper explanation to answer, and if necessary, provide the definition of various terms. And conclude your answer if it's long. If you have used other resources (e.g., Merriam Webster's.) to answer the question, include citations in your answer. You don't need to paraphrase the context of your resources, but make sure that your answer is consistent and complete.
Input: I would tend to write double-l, but Google gives me more single-l, so I'm guessing it's an Atlantic divide thing. And I guess all the other *full words.
Output:
I would say successfull is a typo. Neither Merriam-Webster nor Wiktionary mention it as an alternative spelling. The British National Corpus has 10695 cites for successful and exactly one for successfull. According to OneLook, 33 dictionaries have an entry for successful, but only Wordnik has a few cites for successfull (without a definition). Edit: by popular request, I will add that the adverb successfully is written with two L's. Successfuly would be incorrect.