Rag paper: Papers with a complete or partial content of cotton fibers.

Ragged Left: The term given to right-justified type that is uneven on the left.

Ragged Right: The term given to left-justified type that is uneven on the right.

Railroad Board: A thick, coated paper used for signs; usually waterproof.

Readers Pairs: Two consecutive pages as they appear in printed piece.

Ream: 500 sheets of paper.

Recto: The odd numbered pages (right hand side) of books.

Red Lake "C": A common pigment for paste and liquid red inks.

Reducer: Any substance that softens and reduces the tack of ink.

Reel: The master roll of paper as it comes off the papermaking machine. It is in its original width and is then cut into smaller rolls.

Register: The arrangement of two or more images in exact alignment with each other.

Register Marks: Any crossmarks or other symbols used on layout to assure proper registration.

Right Angle Fold: A term that denotes folds that are 90 degrees to each other.

Roll To Roll: A web press printing process where the roll of paper is printed and stored on a roll to be shipped.

Rub Proof: That stage of printed ink where the maximum dryness is achieved, and the ink will not smudge.

Rubine: A pigment somewhat redder than true magenta.

Run-Around: A term given to copy that accommodates the lines of a picture or other image or copy.

Runability: A term used to describe how well a paper runs on a printing press.

Running Head: A title at the top of a page that appears on all pages of a book or chapter of a book.