If something is comprehensible, a person can understand it without an unusual struggle: the sentences hang together, the steps are in order, the voice is not a mumble. It is about being get-able, not about being simple-minded. A hard science idea can still be comprehensible if someone explains it in a careful way. The word is a little formal; in daily speech people say understandable or “I get it.” Its opposite is incomprehensible — so unclear that you cannot find a way in. Though actually students trip on a lookalike: comprehensive. Comprehensive means wide and full, covering almost everything (a comprehensive list, a comprehensive school in Britain). A comprehensive report can be barely comprehensible if it is long and muddy.