6 ms·

> The clathrate’s “cage” shapes are 12-sided dodecahedrons and 14-sided tetrakaidecahedrons made of silicon atoms... Totally OT but if "dodeca" means 12, why i

> The clathrate’s “cage” shapes are 12-sided dodecahedrons and 14-sided tetrakaidecahedrons made of silicon atoms... Totally OT but if "dodeca" means 12, why isn't 14 just "tetradeca"? What's the "kai" for?

normie3000 5mo ago
kai means "and" I guess like asking why 120 is said "one hundred and twenty" in some dialects. Maybe that's how 14 and 12 are written in Greek.
- frereubu 5mo ago
  Ah I see, thanks!
- HighGoldstein 5mo ago
  The Greek term would be decatetrahedron.
  - normie3000 5mo ago
    Apologies - Ancient Greek!
  - adrian_b 5mo ago
    Ancient Greeks did not say "dekatetra" for 14, i.e. ten-four, but as it is correctly written in TFA, they said "tetrakaideka" for 14, i.e. "four-and-ten", which is actually close to English "fourteen". For example, already Aristotle used "dipoda" (2-feet) for humans and birds, "tetrapoda" (4-feet) for other terrestrial vertebrates and "hexapoda" (6-feet) for insects. After the same model one can say "oktopoda" (8-feet) about spiders and "tetrakaidekapoda" (14-feet) about woodlice.
gapan 5mo ago
As the sibling comment already said "kai" (pronounced ke like in keg) just means "and". So it literally means 4 and 10 sides in greek. But I have often seen it written as τετραδεκάεδρο (tetradecahedron) in greek as well, so without the kai part. I'm not sure why it is 4 and 10 instead of 14 though. It would be more natural in greek that way (δεκατετράεδρο - decatetrahedron). Maybe it is for putting the distinctive part (4) first, or maybe it sounded more "poetic" like that to someone and then it stuck.
- fhars 5mo ago
  Nobody would be so weird as to put the "four" first when pronouncing "14". :-)
  - gapan 5mo ago
    Haha, right!
  - cratermoon 5mo ago
    Four score and seven years ago...
- corkybeta 5mo ago
  Four and twenty blackbirds, baked in a pie. https://en.wikipedia.org/wiki/Sing_a_Song_of_Sixpence https://en.wikipedia.org/wiki/Sing_a_Song_of_Sixpence
- shever73 5mo ago
  I think the three-and-ten, four-and-ten way of expressing numbers is primarily an ancient Greek thing. The modern numbers are expressed differently (δεκατέσσερα / dekatessara for fourteen, for example). In a lot of older European languages 11 and 12 behaved irregularly. You could argue that they do in English too (we don't have oneteen and twoteen). I haven't read of any particular reason for this, but I'd posit that numbers up to twelve were more commonly used in everyday life, so shorter, irregular forms were easier to use and remember. Much like many of the irregular verb forms in spoken language happened because they were so commonly used. The ancient Greek system also gave us triskaidekaphobia - the fear of the number 13.
  - gapan 5mo ago
    Indeed, in ancient greek they put the "δέκα" (ten) part second. Τρία και δέκα (13), τέσσερα και δέκα (14), πέντε και δέκα (15), etc, but 11 and 12 was (and still is in modern greek) irregular, έντεκα (enteka) and δώδεκα (dodeka) respectively.
  - shagie 5mo ago
adrian_b 5mo ago
For the same reason why in English 12 = twelve, but 14 = fourteen. Not all numerals are formed by the same rule. The correspondents of the -teen numbers in Greek were formed similarly with English, after the model of 14 = four and ten = "tetrakaideka". "Tetrakaideka" is a contracted form of 14, normally used in compound words. When "14" was an isolated word, it would have been "tettarakaideka" or "tessarakaideka". These are the forms for the neuter gender, the numeral "4" = "tettara" or "tessara" (depending on the dialect) was changed by declension for other genders and cases. In Ancient Greek numbers bigger than 20, the word "and" = "kai" was usually omitted, but then the bigger number was always the first like in "twenty-four". When "and" was inserted, then the order could also be inverse, like in "four-and-twenty".
NoMoreNicksLeft 5mo ago
Because the Greek word for 12 is something like "though-theka". And the word for 14 is "theka-tessera". Like most European languages, 11 and 12 are special, then it reverts to the "single digit - ten" or "ten - single digit" pattern. "kai" is "and" in Greek.

normie3000 5mo ago

kai means "and" I guess like asking why 120 is said "one hundred and twenty" in some dialects. Maybe that's how 14 and 12 are written in Greek.

frereubu 5mo ago
Ah I see, thanks!
HighGoldstein 5mo ago
The Greek term would be decatetrahedron.
- normie3000 5mo ago
  Apologies - Ancient Greek!
- adrian_b 5mo ago
  Ancient Greeks did not say "dekatetra" for 14, i.e. ten-four, but as it is correctly written in TFA, they said "tetrakaideka" for 14, i.e. "four-and-ten", which is actually close to English "fourteen". For example, already Aristotle used "dipoda" (2-feet) for humans and birds, "tetrapoda" (4-feet) for other terrestrial vertebrates and "hexapoda" (6-feet) for insects. After the same model one can say "oktopoda" (8-feet) about spiders and "tetrakaidekapoda" (14-feet) about woodlice.

gapan 5mo ago

As the sibling comment already said "kai" (pronounced ke like in keg) just means "and". So it literally means 4 and 10 sides in greek. But I have often seen it written as τετραδεκάεδρο (tetradecahedron) in greek as well, so without the kai part. I'm not sure why it is 4 and 10 instead of 14 though. It would be more natural in greek that way (δεκατετράεδρο - decatetrahedron). Maybe it is for putting the distinctive part (4) first, or maybe it sounded more "poetic" like that to someone and then it stuck.

fhars 5mo ago
Nobody would be so weird as to put the "four" first when pronouncing "14". :-)
- gapan 5mo ago
  Haha, right!
- cratermoon 5mo ago
  Four score and seven years ago...
corkybeta 5mo ago
Four and twenty blackbirds, baked in a pie. https://en.wikipedia.org/wiki/Sing_a_Song_of_Sixpence https://en.wikipedia.org/wiki/Sing_a_Song_of_Sixpence
shever73 5mo ago
I think the three-and-ten, four-and-ten way of expressing numbers is primarily an ancient Greek thing. The modern numbers are expressed differently (δεκατέσσερα / dekatessara for fourteen, for example). In a lot of older European languages 11 and 12 behaved irregularly. You could argue that they do in English too (we don't have oneteen and twoteen). I haven't read of any particular reason for this, but I'd posit that numbers up to twelve were more commonly used in everyday life, so shorter, irregular forms were easier to use and remember. Much like many of the irregular verb forms in spoken language happened because they were so commonly used. The ancient Greek system also gave us triskaidekaphobia - the fear of the number 13.
- gapan 5mo ago
  Indeed, in ancient greek they put the "δέκα" (ten) part second. Τρία και δέκα (13), τέσσερα και δέκα (14), πέντε και δέκα (15), etc, but 11 and 12 was (and still is in modern greek) irregular, έντεκα (enteka) and δώδεκα (dodeka) respectively.
- shagie 5mo ago

adrian_b 5mo ago

For the same reason why in English 12 = twelve, but 14 = fourteen. Not all numerals are formed by the same rule. The correspondents of the -teen numbers in Greek were formed similarly with English, after the model of 14 = four and ten = "tetrakaideka". "Tetrakaideka" is a contracted form of 14, normally used in compound words. When "14" was an isolated word, it would have been "tettarakaideka" or "tessarakaideka". These are the forms for the neuter gender, the numeral "4" = "tettara" or "tessara" (depending on the dialect) was changed by declension for other genders and cases. In Ancient Greek numbers bigger than 20, the word "and" = "kai" was usually omitted, but then the bigger number was always the first like in "twenty-four". When "and" was inserted, then the order could also be inverse, like in "four-and-twenty".

NoMoreNicksLeft 5mo ago

Because the Greek word for 12 is something like "though-theka". And the word for 14 is "theka-tessera". Like most European languages, 11 and 12 are special, then it reverts to the "single digit - ten" or "ten - single digit" pattern. "kai" is "and" in Greek.