I

i.e.,
Abbreviation for the Latin id est or "that is"; always followed by a comma.

immigrate
See emigrate, immigrate.

importantly
The “ly” is not needed when used in an introductory clause. Correct: More important you should be on time to the meeting.

in-
No hyphen when it means "not": inaccurate, insufferable. Often no hyphen in other cases, as well: inbound, indoor, inpatient. Some combinations take a hyphen: in-law. Follow Webster’s New World College Dictionary when in doubt.

incorporated
Abbreviate and capitalize as Inc. when used as part of a corporate name. It usually is not needed, but when it is used, do not set off with commas: J.C. Penney Co. Inc. announces... Also, see brand name.

infra-
The rules in prefixes apply, but in general, no hyphen: infrared, infrastructure.

inter-, intra-
The rules in prefixes apply, but in general, no hyphen. Inter- means between or among: interracial, interstate. Intra- means within or inside: intramural, intravenous.

Internet
A decentralized worldwide network of computers that can communicate with each other. If an Internet address falls at the end of a sentence, use a period. (If an address breaks between lines, split it directly before a slash or a dot that is part of the address, without an inserted hyphen.) Although in some cases it may not be necessary, use the http:// protocol at the start of a Web address, as well as other starts, such as ftp://. Also, see Computer terminology and URL.

intra-
See inter-, intra-.

irregardless
A double negative. Regardless is correct.

it’s, its
It’s is a contraction for it is or it has: It’s up to you. It’s been a long time. Its is the possessive form of the neuter pronoun: The company lost its assets.

Ivy League
Brown University, Columbia University, Cornell University, Dartmouth College, Harvard University, Princeton University, University of Pennsylvania, and Yale University.