pon-, posit-, pos-, -poning, -poned, -ponency, -ponent, -ponement, -pound

1. To lay or place (something) on or over something else.
2. To add as a distinct feature, element, or quality: "She superimposed her own interpretation when she retold the story."
3. To put or join as an addition (usually followed by on or upon).
4. In motion Pictures and television; to print (an image) over another image so that both are seen at once: "The credits were superimposed over the opening scene."

1. The placing of one image on top of another, especially placing a photograph over some other graphic.
2. To lay or place (something) on or over something else.
3. To add as a distinct feature, element, or quality: "The teacher superimposed her own interpretation when she retold the story to the class."
4. The principle in library cataloging when new rules are introduced, whereby only entries made after the rules take effect need to conform to the changes, making it unnecessary to recatalog materials processed under the old rules.

New entries are interfiled with the old. The principle was adopted in 1967 by libraries throughout the United States, following Library of Congress practice, when Anglo-American Cataloging Rules were adopted as the national catalog code.