First of all, I am not sure what chikon means. I couldn't find a relation between 'chikon' and Chikungunya viral disease. I couldn't find "chikon" using Google Define or Merriam Webster. So, maybe it's better if you ask your client what this term refers to.

Secondly, the correct Arabic translation for dimethoxy is ثنائي ميتوكسي.

For any medical translations or medical terminology, I would encourage you to use www.alqamoos.org. It's more reliable when it comes to medical terms.


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Note added at 20 hrs (2019-01-31 04:18:57 GMT)
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One more thing: I really doubt that 'chikon' means 'Chikungunya' disease. It could be a component that is combined with dimethoxy", so please double check with your client and alter them.

If you want more info on this disease, please see this page from the World Health Organization

Arabic page:
https://www.who.int/ar/news-room/fact-sheets/detail/chikungu...

English page:
https://www.who.int/news-room/fact-sheets/detail/chikungunya



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Note added at 20 hrs (2019-01-31 04:21:52 GMT)
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آسف
المفروض تكون بالثاء

ثنائي ميثوكسي