if, whether In formal writing, don't substitute "if" for "whether." Right: I don't know whether I'll dress as Michael Jackson for the costume party.
impact Use as a noun, but avoid as a verb when the meaning is "affect." Right: Retrenchment had a devastating impact on UM. Wrong: Retrenchment will negatively impact UM.
imply, infer The speaker implies; the listener infers: Are you implying I'm a liar? From your comments, I infer that you don't plan to give me a raise.
important, importantly Right: More important, they need to raise $1 million. Wrong: More importantly, they need to raise $1 million.
in- Don't use a hyphen when "in" means "not": inappropriate, incomparable. But use a hyphen with words like "in-depth," "in-house" and "in-laws." One word in other cases: indoor, inpatient, infield. Follow Webster's when in doubt.
-in Hyphenate the noun and adjective forms: A break-in was reported to the police. Stanton was a write-in candidate. Use two words otherwise: Listeners should call in after 6 p.m.
incorporated Abbreviate and capitalize when used as part of a company's name, but don't precede with a comma: Town Pump Inc.
infant Term applies to children through 12 months old.
infra- See prefixes entry, but in general, no hyphen: infrared, infrastructure.
in memoriam Not "in memorium."
input Do not use as a verb to describe entering data into a computer. See feedback, input entry.
in-service Example: He gave two in-service workshops. But: The bus was not in service.
in state, out of state Don't hyphenate these words when they stand alone, but hyphenate them when they're compound modifiers: She took a job in state. I traveled out of state this summer. How much is in-state tuition? The number of out-of-state students has increased.
insure See ensure, insure, assure entry.
inter- See prefixes entry, but in general, no hyphen unless added to a capitalized word: interstate, inter-American.
Internet The global network of computers encompassing email, the World Wide Web and more. In body text, use the complete Internet address: http://www.umt.edu. When used as a stand-alone graphic element in brochures and other publications, the http:// protocol may be left off: www.umt.edu. See email, Web.
intra- See prefixes entry, but in general, no hyphen: intramural, intrastate.
it's, its "It's" is the contraction for "it is" or "it has"; "its" is a possessive pronoun: It's too bad you had to visit Missoula when it was 30 degrees below zero. It's been too long since we've gone bowling together. The mountain lion licked its paws.
Appendix A: Punctuation
Appendix B: Ways to Avoid Sexist Language
Appendix C: Building Names: UM and Missoula College (formerly College of Technology)