Okay, the user wants me to translate "sub-grade" into Arabic. Let me check the rules again. The first rule says to translate all content into Arabic. The second rule states that if the content is already in Arabic, leave it as is. The third rule is to provide only the translation without any explanations.
So, "sub-grade" isn't in Arabic, so I need to translate it. The term "sub-grade" can be a bit tricky. In academic contexts, it might refer to a lower grade or a subdivision of a grade. The direct translation could be "درجة فرعية" which literally means "subordinate grade" or "sub-grade." Alternatively, depending on the context, it might be "درجة ثانوية" meaning "secondary grade." But I need to make sure which term is more commonly used in Arabic academic settings.
I should verify if there's a standard translation for "sub-grade" in educational contexts. If I'm unsure, "درجة فرعية" seems safe as it directly translates to "sub-grade." I'll go with that unless there's a more appropriate term. Since the user didn't provide context, sticking to the direct translation is the safest bet. Also, the user wants only the translation, so no explanations. Just the Arabic word.