What is a definition of block style?

Block style refers to style of overall paragraph formatting in a typewritten letter, usually a business letter or a letter of formal correspondence. The work block is used because the appearance of such a letter creates the effect, visually, of "solid blocks" of Words on the paper, in particular, solid (dark) horizontal blocks. (In graphic design and in typography, even the overall appearance of letter and Word groupings is said to have varying shades of color, ranging from light to dark. By extension, when Words and sentences are grouped into a paragraph, that paragraph can be said to have a "dark color" (solidness or blockiness) relative the background on which they appear).

At the very least, the style specifies that all paragraphs of the body text of the letter have no indentation of the first line of the paragraph.

There are several other formatting conventions commonly practiced in block style, with no particular convention being considered more correct than another. These variables include: a preference for the single-spacing of all lines of the letter; full-justification of all body-text lines, if possible; left-justification (flush with the left margin) of all non-body-text lines in the letter (e.g., salutation, closing, signature, etc.); and left-justification of the name and address of the addressee, of the sender, and/or of the date line.