What words start with the prefix op?

Here are some words that start with the prefix "op":

Common words:

* oppose

* opinion

* operate

* opportunity

* opposite

* optical

* optimistic

* opium

* open

* opera

* operation

* operator

* optics

Less common words:

* opalescent

* opiate

* opulent

* oppose

* oppress

* optic

* optimal

* optimism

* opus

* oratorio

* option

* optional

Medical terms:

* ophthalmology

* osteoporosis

* operative

* optometrist

* optometry

Other:

* op art (optical art)

* op-ed (opposite the editorial page)

This is not an exhaustive list, but it gives you a good starting point.