Not entirely: The root of Sipra[Heb.: Sifrei], is Sofer and means to
count, as well as to write. Hence a sofer is s scribe,and a sefer is
that which is written by a scribe, especially a Torah Scroll. Ketava
is derived from the 3rd Person Masculine singular verb,which means he
wrote, and as a noun means any thing that is written,whether an
igret[leter], or a sefer;ketava;book]. Hence both have in more modern
times been used synonomously to mean a book,especially, any of the
books of the Holy Scriptures. I hope that this is an adequate answer
to your question. If not, perhaps someone who is more knowlegeable
than this poor old country bumpkin, can answer your questionm a little
more completely, and adequately. Yisrael Ben-Avraham Ben-David
Foreman