do we have to be writing books to be writers?

i have have had several small articles published,(one even was reprinted in a column, that was syndicated, so it was reprinted in over 5,000 newspapers in US) and other have had poetry published, and many here have written a theis, (which their university has on record somewhere) some, have disertations.

and if if you include my personal letters in my writing, i have written alot, but never a book --(but i am toying with the idea.) but if i do a book, it will be a thin one, and technical. (i am thinking about doing a knitting book.)

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my other obsession