Hi Aggeliki. One is used in verbal sentences, the other in nominal sentences (non verbal) ما is used in a nominal sentence -- ما اِسمك؟. ماذا in a verbal sentence --ماذا فعلت اليوم؟.

ما + noun ماذا + verb It's not about what kind of sentence you're using, it's about what kind of word you're putting, wether a noun or a verb.

actually, they're very similar in the sense they both can mean "what". but each is used based on the context. In current colloquial arabic, majority use ايش or شنو or ايه or شو for "what". very rarely you'd hear ماذا. ما has other meanings, more commonly nowadays as to negate sentences. in some cases you'll only tell the difference by context, if it's written in formal arabic or colloquial. e.g., ما قرأت it can mean: 1. I haven't read. (in colloquial). 2. What I've read. (in formal fus-ha)

...ماذا أداة استفهام أما ما قد تأتى أداة استفهام أوأداة شرط أو اسم موصول أو أداة نفى