Subject
The main thing you talk about in your language becomes the subject of the sentence.
しゅご
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
主語をハッキリさせてくれないかな。
Can you make the subject clear?
この主語を明かくにする新サービスは、本当に役に立つ。
This new service that clarifies the subject is very useful.
日本語は、主語ー目的語ー動詞の言語ですが、英語は主語ー動詞ー目的語の言語です。
Japanese is a subject-object-verb language whereas English is a subject-verb-object language.