Today I corrected a translation into Italian on WiktionaryZ - forbici ... it had to be forbice. Of course, since Italian is not my mother tongue, even if I am sure about a change I check it with other dictionaries. In that way I found several related terms which I then wanted to add as relations. Big surprise: there are only four possible relation types and all are connected to the GEMET multilingual thesaurus that was the first contents of WiktionaryZ. Therefore I could not add these related words, since they simply did not match this scheme.
Then I thought about technical terminology and how a term can be used in different domains ... well I could not even add those right now, since it would require double and triple work afterwards ... or better: consider what happens if we have some 10,000,000 entries and then, for my work I search for a term being my translation of a specific domain - for example the automotive industry. Let's say I get only 50 results for the term I search, all mixed up ... no possibilty to have them filtered by domain ... that would cost me in the worst case 50 clicks to understand if one of the terms matches or not .... considering that clicking through 50 matches, reading the definition will at least take 20 minutes (and that is even fast to my opinion) and considering a price of only 30 EUR/hour it would mean that the search of a single term for a translator costs 10 EUR ... well: that is simply too much - not having domains in WiktionaryZ for practical use means that WiktionaryZ simply would be useless.
Of course there are many other reasons for having domains and I'd say not one reason for not having them ....
I also considered to use semantic web on my wiki ... if these terms were translated with a wikidata structure without the attribution of a domain semantic web would be simply useless for a correct search.
No ... we need it ... we definitely need them asap. And yes, you who are reading this, tell us your opinion - how would domains (like: technics, medicine, biology etc. etc.) be helpful for your use.
Thanks!