Common words:
* primary: most important, main
* private: belonging to or intended for the use of a particular person or group, not public
* primitive: belonging to an early stage of development, simple
* prize: something won in a competition or as a reward
* price: the amount of money for which something is sold
* print: to produce an image or text on paper
* prior: existing or happening before something else
* priority: something that is more important than other things
* privilege: a special right or advantage available only to a particular person or group
* privacy: the state or condition of being alone or undisturbed
Less common words:
* primate: a member of the order of mammals that includes humans, apes, and monkeys
* primogeniture: the state of being the firstborn child
* primordial: existing at or from the beginning of time
* pristine: perfectly clean and spotless, untouched
* prickly: covered with sharp points, irritating
* privy: having secret knowledge or information
* prohibit: to forbid something
* prolific: producing a large amount of something
* propensity: a natural tendency to behave in a particular way
These are just a few examples, and there are many other words that begin with "pri".