Hi Tavie,
I'll add a few words to Koen's reply about abbreviations and conditional entropy.
Many medieval abbreviations work by replacing a frequent sequence (e.g. bigram / trigram) with a single symbol. This results in a shorter text because the sequence is frequent (if it were infrequent, the effect would be minimal) and because of course the original sequence is longer than the single symbol that replaces it. One way to see conditional entropy is that it measures the relative quantity of frequent bigrams: very frequent bigrams result in lower conditional entropy. Consequently, removing frequent bigrams tends to increase conditional entropy.
For instance, this text reads:
et gemitibus incessanter clamemus
but this was rendered as something like:
2 gemitib9 incessant^ clamem9
The abbreviated text is 4 character shorter than the actual text (about 10% shorter).
"Et" (and) is the most frequent Latin word. When you see an 'e', you can expect that the next letter will be 't' and you will often be right. The abbreviation that I have rendered as "2" represents the whole word "et", so this removes a good chance to guess the next letter given the previous one. If _ represents space, the sequence _et_ becomes _2_, instead of three "easy" guesses (_e,et,t_), you get only two (_2,2_)
Similarly, "us" is a frequent bigram at the end of Latin words. Again, guessing that 'u' is followed by 's' is a good bet. But this bet is made impossible if 'us' is rendered as the single symbol '9'.
Also, abbreviations were not applied consistently: in the same text you can find 'et' and '2', as well as 'gemitib9' and 'gemitibus'. Since the use of abbreviations was something that the scribe could apply or not at will for each word occurrence, guessing the next character is made even harder: you don't know if any particular word token will be abbreviated or not. One of the meanings of 'entropy' is exactly 'lack of order or predictability' and scribes could be highly unpredictable in their use of abbreviations.
Finally, this subject was discussed by Lindemann and Bowern, who compared actual abbreviated historical texts in a few languages with normalized, unabbreviated versions (You are not allowed to view links. Register or Login to view.):
I'll add a few words to Koen's reply about abbreviations and conditional entropy.
Many medieval abbreviations work by replacing a frequent sequence (e.g. bigram / trigram) with a single symbol. This results in a shorter text because the sequence is frequent (if it were infrequent, the effect would be minimal) and because of course the original sequence is longer than the single symbol that replaces it. One way to see conditional entropy is that it measures the relative quantity of frequent bigrams: very frequent bigrams result in lower conditional entropy. Consequently, removing frequent bigrams tends to increase conditional entropy.
For instance, this text reads:
et gemitibus incessanter clamemus
but this was rendered as something like:
2 gemitib9 incessant^ clamem9
The abbreviated text is 4 character shorter than the actual text (about 10% shorter).
"Et" (and) is the most frequent Latin word. When you see an 'e', you can expect that the next letter will be 't' and you will often be right. The abbreviation that I have rendered as "2" represents the whole word "et", so this removes a good chance to guess the next letter given the previous one. If _ represents space, the sequence _et_ becomes _2_, instead of three "easy" guesses (_e,et,t_), you get only two (_2,2_)
Similarly, "us" is a frequent bigram at the end of Latin words. Again, guessing that 'u' is followed by 's' is a good bet. But this bet is made impossible if 'us' is rendered as the single symbol '9'.
Also, abbreviations were not applied consistently: in the same text you can find 'et' and '2', as well as 'gemitib9' and 'gemitibus'. Since the use of abbreviations was something that the scribe could apply or not at will for each word occurrence, guessing the next character is made even harder: you don't know if any particular word token will be abbreviated or not. One of the meanings of 'entropy' is exactly 'lack of order or predictability' and scribes could be highly unpredictable in their use of abbreviations.
Finally, this subject was discussed by Lindemann and Bowern, who compared actual abbreviated historical texts in a few languages with normalized, unabbreviated versions (You are not allowed to view links. Register or Login to view.):
Lindemann and Bowern wrote:The usage of abbreviations and special characters has the effect of raising the conditional character entropy of the English, Icelandic, and Latin texts and taking them further from the values we find for Voynichese.
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