- (initialism) That is; in other words; that is to say.
- The three U.S. states on the west coast (i.e., Washington, Oregon and California) have favorable climates.
- i.e. is used to explain, clarify or rephrase a statement rather than listing options, in which case e.g. should be used.
- Often confused with e.g.
- American English prefers a comma after i.e.; in British English a comma does not follow i.e. 
- Opinion is mixed about whether the abbreviation should be italicized, or whether there should be a separating non-breaking space as in i. e.. However, the AMA manual of style recommends to forgo italic on terms long since naturalized into English and not to separate abbreviations (see "Abbreviations" on wikipedia).
- ie: is often found in current usage, and is perhaps now considered acceptable.
i.e. differs from viz. in that what follows merely restates what was said in other words, rather than expanding upon what has already been said; and from e.g. in that completeness or near-completeness is suggested, rather than a small selection of examples.
- Abbreviation of isto es.
- Equivalent in meaning to English i.e..