pan- In general, no hyphen when used as a prefix, unless it is followed by a proper name: panchromatic, panhandle; pan-Hellenic. See Words Formed with Prefixes under General Style Preferences.

parallel, paralleled, paralleling

part-time, part time Hyphenate as an adjective before a noun: She is a part-time student. Otherwise, leave as two words: He attends college part time.

pastime This word combines pass (not past) and time, and is spelled with a single t.

people, persons, peoples The traditional view is that persons is used for smaller numbers (three persons) and people with larger ones (millions of people). But today people is used even for small groups (only three people were there); this is acceptable and preferred in all references.

People also is a collective noun that takes a plural verb when used to refer to a single tribe, race, or nation: The Navajo people are united. In this sense, the plural is peoples: The peoples of Africa speak many languages.

-persons Do not used coined words such as chairperson or spokesperson in regular text. Neutral words include leader or representative. Also see chair.

percent, % Use numerals (with decimals, not fractions, when needed) and spell out percent in running text: a 4 percent increase, a 2.5 percent decrease. Use the percent sign (%) in tabular or graphic promotional materials.

period of time, time period Avoid these phrases. Try period or time instead.

phenomenon (singular), phenomena (plural)

planning Avoid the redundant future planning.

podcast One word, no hyphen.

policymaker, policymaking

politics Usually takes a plural verb: His politics are his own business. As a study or science, it takes a singular verb: Politics is a demanding profession.

post- In general, no hyphen when used as a prefix, unless it is followed by a proper name: postdate, postelection, postmodernism, postoperative, postmortem, postscript; post-Vietnam. See Words Formed with Prefixes under General Style Preferences.

postbaccalaureate No hyphen. Also: postgraduate, postdoctoral; but post-master’s, to differentiate from a mail postmaster.

practical, practicable, possible What is practical is fit for actual use. What is practicable is capable of being done; it’s feasible. To help distinguish between these two words, think of practical as a synonym of useful, and practicable as a synonym of feasible. What is possible might be capable of happening or being done, but there is some doubt.

pre- In general, no hyphen when used as a prefix, except to separate two e’s or when it is followed by a proper name: precondition, predate, preflight, pregame, prehistoric, prejudge, prenatal, pretax; pre-eminent, pre-empt; pre-Columbian. See Words Formed with Prefixes under General Style Preferences.

precalculus No hyphen.

precollege No hyphen.

premier, premiere Premier is top quality: She went to the premier resort on the Riviera. Premiere is a first performance: He attended the premiere of the new play.

prerequisite No hyphen. Also: corequisite.

presently Use it to mean “in a little while” or “shortly,” but not to mean “now.”

presidency Always lowercase.

presiding officer Always lowercase.

preventive Although the corrupt form preventative (with the superfluous syllable in the middle) is fairly common, the strictly correct form is preventive. (Chicago Manual of Style)

prime time (n.), prime-time (adj.)

principle, principal A principle is a natural, moral, or legal rule: the principle of free speech. The corresponding adjective is principled: a principled decision. A principal is a person of high authority or prominence (a school principal) or a loan amount requiring repayment (principal and interest). A principal role is a primary one.

prior to, before The word before is less stilted for most uses and generally preferred. The phrase prior to may be used when a notion of requirement is involved: The fee must be paid prior to the exam.

pro- Use a hyphen when combining with words to indicate “in favor of” or when followed by a proper name: pro-business, pro-labor, pro-war; pro-Canadian. Otherwise, no hyphen: proactive, pronoun. Except in quotations, do not use the polemical terms pro-choice and pro-life. Latin terms are two words even when they precede what they modify: pro bono, pro forma, pro rata, pro tem. See Words Formed with Prefixes under General Style Preferences.

process of, in the You can almost always delete this phrase without affecting the meaning