b) you can use something like > \def\zwj{\char"200d} in your XeTeX source file... > > That is not a good idea. If you need ZWNJ rarely, that might be a good solution but if you typeset Persian, then you find that you have to type lots of ZWNJs. Indeed using ZWNJ in Persian typography is a must. For instance writing میداند or می داند instead میداند is discouraged in good Persian typography.
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