I meant “a topic withing a course you follow” like a “field” such as studying asian cultures and one of the fields you study is buddhism.
Was my interpretation correct? Should I add a synonym?
Problem is I am not a native English speaker, so maybe I used the wrong English word?
I am always reluctant to add synonyms because I do not want to study the wrong meaning of something.
Any advice is welcome. 
Thank you.
It is not a subject of sentence, but more like a subject of conversation, or studying. Jisho translates it as “(school) subject; curriculum; course” Topic would be 題
As for english, I am also not a native speaker, but I would explain the difference as “subject” being broad category of everything related, while “topic” is as specific as it can get. “Math” is a subject. “Addition” is topic.
Even the kanji mean “science” + “see”, like you are looking at science in general and you see wide perspective. The kanji for topic consists of more specific things. It is just few levels ahead of you, so you will get to it soon.
Okay, thank you! 
Honestly, if you know what you mean by “topic,” I think it’s probably fine. The only thing to be careful of is that the way you think of “topic” when looking at “科目” doesn’t change into something that 科目 isn’t.
I’m a native English speaker but will often forget words, though I still remember the concepts. There are times where I’ll be like, “Okay, I know x isn’t the right word, but it’s the closest I can currently come up with to the concept I’m thinking of, and that concept is what this kanji/word is,” and while I won’t add that word as a synonym, I will take a sec to think about whether the concept truly does match the kanji/vocab, even double-checking in a J>E or J>J dictionary if I have to, and then I’ll mark it right if it does or let it stay incorrect if it doesn’t.
You’re here to learn Japanese, not how to translate it into English. Hell, even if your goal was translation, you’re still allowed to look things up to double-check and/or try to find better glosses than the ones you can think up on your own while translating something, no matter how proficient you get in Japanese.
Whenever I wonder if I should add something as a synonym, I always check jisho.org
In this case, it doesn’t list “topic” among meanings, so, I would be careful about adding it. But in some cases, it did have the meaning that I’ve entered (and that WK didn’t accept) – in such cases I always add the meaning as a synonym.
Thank you all! My native language only has one word for both “topic” and “subject”, therefore I often make mistakes with such words since I don’t know what the difference is.
You can also add synonyms in your native language too. I think better than looking up the English would be looking up 科目 and see how it’s actually used in Japanese. Also if english is giving you trouble just look at it as expanding your english vocabulary too.
