'Advisor' vs. 'Adviser'
A centuries-old rivalry
What to KnowThere is no difference between adviser and advisor besides spelling, and both are acceptable for someone who gives advice. Some people, though, feel that advisor is more formal. Advisor tends to be used for people having an official position—for example, an advisor to the president.
Adviser is the overall favorite, based on large swaths of data available on the Internet.
The words adviser and advisor both refer to someone who advises—that is, broadly, someone who offers advice. Both spellings date to the 1500s, with adviser being used several decades before advisor.
Their origins are slightly different, and only in the obvious way: the -or suffix in advisor is ultimately from Latin, while the -er suffix in adviser is ultimately Germanic.
Of note is the fact that in many cases one or the other is used as part of a person's professional title: the United Nations Office of Military Affairs is headed by the Military Adviser. Sometimes a single organization will use both: the United States government has both a National Security Advisor and a Council of Economic Advisers.
Many publications don’t much care how the adviser/advisor writes the title: they go with their own preferred style. Although the U.S. government refers to advisors in discussion of the National Security Council and reference to the National Security Advisor, national news organizations overwhelmingly prefer adviser in the same contexts.
This is an example of how English spelling can be tricky. Sometimes a pair of words will be spelled slightly differently, and this will signify that one word is more common in one country than another (as with British theatre & American theater). Sometimes two words will be spelled slightly differently, and this will signify that they are totally different words with totally different meanings (as with stationary & stationery). And sometimes words will be spelled slightly differently, and this will signify that they are just two versions of the same word (as with adviser & advisor).
What does all this mean for which word you should choose? Based on the current usage you are safest using adviser, rather than advisor (although we can once again stress this means it is more likely to be preferred by a spellcheck or usage manual, which is not the same as saying that one is right and the other is wrong).
