"My boyfriend designs clothing."
Translation:Il mio fidanzato disegna abiti.
That's a very good question. I'm no where close to proficient in Italian, but my guess would be that 'disegna vestiti' (i.e., designs clothes) refers to the person designing clothing in general (he owns a company that designs apparel). Whereas, 'designa i vestiti' (i.e., 'designs THE clothes') would refer to designing specific clothing (he designed my specific outfit).
I google the phrase, and it appears "disegnare vestiti" is treated like a single verb to mean one is a clothing designer. I suspect you could use it if the expression was "my boyfriend is designing the clothing," for instance, if he were designing clothes for a particular event. But I'm not Italian. https://context.reverso.net/translation/italian-english/Disegnare+i+vestiti
The meaning of the different words for clothes sometimes get blurred, - but basically it's something like this:
Abbigliamento = clothing, - a very general and broad term for clothes.
Abiti = formal dresses / gowns and suits / glad rags
Vestiti = clothes.
"Il mio fidanzato disegna abbigliamento" was approved when i tried it 8 Sep. 2019.
Unless it's a specific family member, you need it. http://www.italianlanguageguide.com/italian/grammar/possessive-adjective.asp
The singular family nouns are an exception and there is no definite article (mio padre, tua madre, sua moglie, nostro fratello, tuo zio, suo cugino, ...)
Whereas in the plural the definite article is necessary (i miei fratelli, le mie sorelle, ...)
PS: "fidanzato" is not a family member, so "il mio fidanzato" is correct
Are you certain you worded the phrase correctly otherwise? I just used 'vestiti' and it was accepted. "Il mio fidanzato designa vestiti." I missed it the first time around because I though 'fidanzato' was considered a relation that did not take the direct object … I was wrong! I mean, they aren't even married!