Could 十角形、九角形、七角形 be read as デカゴン、ノナゴン、ヘパタゴン？ As per dic.yahoo.co.jp the following four geometric figures seem to be read as (ateji / gairaigo) ( _decagon_ , _nonagon_ , _heptagon_ , _dodecagon_ ). As per the same dictionary, all the other sided figures that have less than 12 sides, ((triangle ---> 6-sides) + octagon + 11-sides), are read using each kanji's standard So, are these readings ok? **{}** {} <\--- for some reason, normal reading. **{}** **{}** {} <\--- for some reason, normal reading. **{}** Are those less commonly known English names (the only one an _English_ native speaker might know is "decagon") for geometric shapes burrowing their way into the Japanese language as "ateji / gairaigo"? _Or_ , is it that I'm not understanding the *dic.yahoo.co.jp" dictionary, and "" is a straight-up normal counter that is read with standard

No, those `-` words are basically rare loanwords and they're not used in ordinary math classes. (Of course is famous as the name of a building.) The dictionary entries you linked just say that the katakana word **means** , etc. They do not say that is read as , etc. does not seem to be in the same dictionary, but it's simply because the rule is fairly simple and the meaning of is too obvious to Japanese readers.

* :
* :
* :
* :
* : /
* :



... and so forth.

can be replaced with .