Several, such as 'The Communist Manifesto' were written in collaboration with Friedrich Engels.
Dave and Larry wrote a book together, Dave is the main author and Larry is the coauthor.
coauthor
no.
According to the sources I've found on a quick search, you should hyphenate 'coauthor', i.e., it would better be: "co-author".
The word coauthor is a noun. The plural noun is coauthors.
Generally co-author should be hyphenated, but the relaxed rules of modern times often present coauthor as one word
Yes.
Examples of co are cooperate, coworker, coauthor and so on.
Yes, Karl Marx has 7 kids.
Karl Marx has 7 children
johnjay
Karl Marx was born on November 12, 1897.