LIE - To be in a horizontal position.
LIP - Either of the two fleshy protrusions around the opening of the mouth.
PEN - An enclosed area used to contain domesticated animals, especially sheep or cattle.
PEP - To inject with energy and enthusiasm.
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.
NIP - A small quantity of something edible or a potable liquor.
NIL - Nothing; zero.
LINE - A path through two or more points (compare 'segment'); a continuous mark, including as made by a pen; any path, curved or straight.
PILE - A dart; an arrow.
PINE - Any coniferous tree of the genus Pinus.
PIPE - A rigid tube that transports water, steam, or other fluid, as used in plumbing and numerous other applications.
LIEN - A tendon.
NIPPLE - The projection of a mammary gland from which, on female mammals, milk is secreted.