I’ve used several sources over the years to clarify the uses of e.g. and i.e., including my favorite grammar source, Grammar Girl. Here is a short post outlining the usages:
e.g.—Latin for exempli gratia, “for example.”
After e.g., a list of examples follows. Note that the list is not meant to be an all-inclusive list of examples.
Remember that the “e” in e.g. stands for “example.”
Example: He plays woodwind instruments (e.g., flute, clarinet, alto saxophone).
i.e.—Latin for id est, “that is.”
After i.e., an explanation or clarification follows. The explanation or clarification is implied to be all-inclusive of the idea.
Remember that the “i” in i.e. stands for “in other words.”
Example: I prefer to use computer operating systems designed by Apple (i.e., OS X and iOS).
A few more details:
- Both i.e. and e.g. are abbreviations so periods after each letter are required.
- Although i.e. and e.g. are Latin words, the terms are accepted as part of the English language. The terms need not be italicized.
- The majority of style guides I have consulted either prefer or require a comma following i.e. and e.g. when used as described above.
One final technical issue to address is the inclusion of “etc.” after either i.e. or e.g. (The term “etc.” is Latin for “et cetera” and means “and the rest.”) When using e.g., using etc. is probably unnecessary, since “for example” implies that the list of examples is not all-inclusive. When using i.e., using etc. is likely never appropriate, since the list following is an all-inclusive idea.