In typography, rivers, or rivers of white, are gaps in typesetting, which appear to run through a paragraph of text, due to a coincidental alignment of spaces. The rivers can occur regardless of the spacing settings, but are most noticeable with wide inter-word spaces caused by full text justification or monospaced fonts. Rivers are less noticeable with proportional fonts, due to narrow spacing. Another cause of rivers is the close repetition of a long word or similar words at regular intervals, such as "maximization" with "minimization" or "optimization".