Answer: Are there any specific rules for using "unbeknown" versus "unbeknownst"?
...with examples from Stargate Atlantis, Harry Potter, and House...
writinginct asks: Are there any specific rules for using unbeknown versus unbeknownst?
Both unbeknown and unbeknownst are in widespread standard use and have been for many years. However, there are two main things to keep in mind when using either of the words: region and use with the preposition to.
Region
While both words are acceptable in the English language, different regions have a certain proclivity toward one or the other. According to the Cambridge International Corpus, 3.0 instances of unbeknown compared to only 0.9 instances of unbeknownst per ten million words appeared in British English texts, while 4.1 occurrences of unbeknownst per ten million and only 1.0/10,000,000 occurrences of unbeknown showed up in American English texts.
Basically, American characters are more likely to use unbeknownst, while British characters will probably go with unbeknown. When writing, always keep in mind where your characters are from, and choose the more accepted usage.
Use with To
Whichever word you employ, both unbeknown and unbeknownst should almost always be used in conjunction with the preposition to.
...a crisis unbeknownst to the Atlantis team.
Neville's latest attempt at spell making had, unbeknown to him, caught his robes on fire.
Unbeknownst to his team, Dr. House was visiting his patient.
Why is to an essential part of the unbeknown(st) construction? The root word basically means "occurring or existing without the knowledge of a specified party." While research suggests to is "usually" used in conjunction, how else would one point to that specified party if not with to?
When Daniel brought up the intricacies of Unas language, he was faced with a roomful of blank stares. Apparently the concept was virtually unbeknownst.
In sentences like this, you would use unknown instead of unbeknown(st).
Summary
You can use both unbeknown and unbeknownst fairly interchangeably. If you simply keep in mind the region the character is from, and try to steer clear of unbeknown(st) without the preposition to, you should be good to go.
Resources:
Exploring Unbeknownst
Merriam-Webster's Dictionary of English Usage (Merriam-Webster, Inc)
Unbeknown or Unbeknownst?
writinginct asks: Are there any specific rules for using unbeknown versus unbeknownst?
Both unbeknown and unbeknownst are in widespread standard use and have been for many years. However, there are two main things to keep in mind when using either of the words: region and use with the preposition to.
Region
While both words are acceptable in the English language, different regions have a certain proclivity toward one or the other. According to the Cambridge International Corpus, 3.0 instances of unbeknown compared to only 0.9 instances of unbeknownst per ten million words appeared in British English texts, while 4.1 occurrences of unbeknownst per ten million and only 1.0/10,000,000 occurrences of unbeknown showed up in American English texts.
Basically, American characters are more likely to use unbeknownst, while British characters will probably go with unbeknown. When writing, always keep in mind where your characters are from, and choose the more accepted usage.
Use with To
Whichever word you employ, both unbeknown and unbeknownst should almost always be used in conjunction with the preposition to.
...a crisis unbeknownst to the Atlantis team.
Neville's latest attempt at spell making had, unbeknown to him, caught his robes on fire.
Unbeknownst to his team, Dr. House was visiting his patient.
Why is to an essential part of the unbeknown(st) construction? The root word basically means "occurring or existing without the knowledge of a specified party." While research suggests to is "usually" used in conjunction, how else would one point to that specified party if not with to?
When Daniel brought up the intricacies of Unas language, he was faced with a roomful of blank stares. Apparently the concept was virtually unbeknownst.
In sentences like this, you would use unknown instead of unbeknown(st).
Summary
You can use both unbeknown and unbeknownst fairly interchangeably. If you simply keep in mind the region the character is from, and try to steer clear of unbeknown(st) without the preposition to, you should be good to go.
Resources:
Exploring Unbeknownst
Merriam-Webster's Dictionary of English Usage (Merriam-Webster, Inc)
Unbeknown or Unbeknownst?