Read the reference list of almost any scientific paper and you'll see the same two words over and over: "et al." Most readers know it means "and the others". Fewer know it's Latin, or why it has one period (a full stop, in British English) and not two. Latin abbreviations sit in plain sight in emails, footnotes, clocks and price labels, and the most mixed-up pair of all is e.g. and i.e.
e.g. vs i.e.
They aren't interchangeable. e.g. is exempli gratia, "for the sake of an example". It gives one or more examples from a bigger group: "citrus fruit, e.g. lemons". i.e. is id est, "that is". It restates, narrowing to the one thing you mean: "the smallest continent, i.e. Australia".
A quick test: if you could swap in "for example", use e.g. If you could swap in "in other words", use i.e. You may have learned "example given" and "in essence" as memory tricks. They work, but they're English mnemonics, not what the letters stand for.
etc. and et al.
etc. is et cetera, "and the rest". et al. is short for et alii (or et aliae, et alia), "and others", and it's used for people, especially authors. Et is a complete Latin word meaning "and", so it never takes a period. Only al. is shortened.
Clocks and calendars
a.m. is ante meridiem, "before midday", and p.m. is post meridiem, "after midday". Meridiem is a form of meridies, "midday", built from medius, "middle", and dies, "day". AD is anno Domini, "in the year of the Lord". It doesn't mean "after death". Its partner BC isn't Latin at all: it's English, "before Christ". c. or ca. before a date is circa, "around".
Letters, notes and footnotes
- P.S.: post scriptum, "written after".
- N.B.: nota bene, "note well".
- cf.: confer, "compare". It sends you to a source to compare, not simply to "see".
- ibid.: ibidem, "in the same place", meaning the same source as the note before.
- viz.: videlicet, "namely", from videre licet, "it is allowed to see". The z stands for a medieval scribe's shorthand mark for the ending -et.
Latin hiding in symbols
Some Latin abbreviations no longer look Latin. No. is numero, "in number", which is why it has an o. lb is libra, a Roman unit of weight, and the £ sign is a decorated L for the same word. Q.E.D., quod erat demonstrandum, "which was to be shown", is the Latin translation of a Greek phrase Euclid used to end his proofs. And [sic], sic, "thus", marks something, usually an error, that really is in the original. It isn't an acronym, whatever the internet says.
Common mistakes
- Using i.e. before examples. If the list isn't complete, you want e.g.
- Writing "and etc." Et already means "and".
- Ending an e.g. list with etc. Many style guides call it redundant: e.g. has already told the reader there are more.
- Writing "et. al." Et is a whole word, so it takes no period.
- Writing "ante meridian". The Latin is meridiem.
Frequently asked questions
What is the difference between e.g. and i.e.?
e.g. (exempli gratia) gives examples; i.e. (id est, "that is") restates or specifies exactly what you mean.
What does et al. stand for?
Et alii, "and others" (et aliae or et alia for other genders). It's used to shorten a list of people, usually authors.
Do you put a comma after e.g. and i.e.?
Style guides differ. Many US guides put a comma after both; many British publishers leave it out. Pick one and stay consistent.
What do a.m. and p.m. stand for?
Ante meridiem and post meridiem: "before midday" and "after midday".
Try it
Say the full Latin before you flip each card. Then recall: which abbreviation would you put before "Australia" in "the smallest continent, ___ Australia", and what are the two Latin words behind it?