To make things simple:
In the Order of the Arrow, a Scouter is always an adviser, not an advisor.
Now, you may wonder, you have often seen the appearance of advisor in documents, online, and maybe messages from your friends and colleagues. To be clear, this spelling is always incorrect. Adviser is the only correct usage in the Order of the Arrow.
Additionally, you may be familiar with the Venturing program, and you may have seen those groups use the word advisor. Well, in their case:
In Venturing and Exploring, an adult is always an advisor, not an adviser.
Undoubtedly, this can be the source of a lot of confusion, and Venturers getting involved in the Order of the Arrow may find it perplexing. It is. It is entirely possible for an adult Venturing advisor to be an adviser in the Order of the Arrow.
The use of advisor dates back to the earliest days of the Exploring program. In addition, the use of adviser has its roots back to the beginnings of the Order of the Arrow.
The English language, with its historic borrowing of words from other languages, combined with variation of spellings across dialects, invites this sort of challenge.
It should be noted that in everyday English, either spelling is acceptable. Adviser is thought to be an older spelling than advisor, and generally remains more prevalent. However, neither word is “better” than the other.
The only difference in Scouting is the historic use of the word in different programs. So whether you are talking about an OA event or a Venturing event, it is good to know the proper use.
For additional perspective on the Order of the Arrow’s use of adviser, see this link on the National website.