PEN - An enclosed area used to contain domesticated animals, especially sheep or cattle.
PER - For each.
PIE - A type of pastry that consists of an outer crust and a filling.
PIN - A small device, made (usually) of drawn-out steel wire with one end sharpened and the other flattened or rounded into a head, used for fastening.
RIP - A tear (in paper, etc.).
URN - A vase with a footed base.
NIP - A small quantity of something edible or a potable liquor.
REP - Short form of reputation.
PUN - To beat; strike with force; ram; pound, as in a mortar; reduce to powder.
PIER - A raised platform built from the shore out over water, supported on piles; used to secure, or provide access to shipping; a jetty.
PINE - Any coniferous tree of the genus Pinus.
PURE - Free of flaws or imperfections; unsullied.
RIPE - Ready for reaping or gathering; having attained perfection; mature; -- said of fruits, seeds, etc.; as, ripe grain.
RUIN - Construction withered by time.
RUNE - A letter, or character, belonging to the written language of various ancient Germanic peoples, especially the Scandinavians and the Anglo-Saxons.
RIPEN - To grow ripe; to become mature, as in botany: grain, fruit, flowers, and the like; as, grapes ripen in the sun.
PRUNE - A plum.
INURE - To take effect, to be operative.
PUNIER - Comparative form of puny: more puny.
UNRIPE - Not ripe.