Vigorous writing is concise. A sentence should contain no unnecessary words, a paragraph no unnecessary sentences, for the same reason that a drawing should have no unnecessary lines and a machine no unnecessary parts. This requires not that the writer make all sentences short, or avoid all detail and treat subjects only in outline, but that every word tell.
– William Strunk Jr. The Elements of Style, Fourth Edition, p. 23.
A great quote from a book that should be studied by every English reader.
The original 1918 edition is online for free.