Sceptic vs. skeptic
In most of their senses, there is no difference between skeptic and sceptic. Skeptic is the preferred spelling in American and Canadian English, and sceptic is preferred in the main varieties of English from outside North America. This extends to all derivatives, including sceptical/skeptical and scepticism/skepticism. There is an exception, though: In reference to some 21st-century strains of scientific skepticism, writers and publications from outside North America often use the spellings with the k.
http://grammarist.com/spelling/sceptic-skeptic/
