This is the 3746th most frequent Japanese word.
すじ
"すじ" (suji) means "muscle," "fiber," "thread," "line," "logic," or "plot," depending on context.
In this sentence, 'すじ' refers to the 'theme' or 'main point' of a story.
彼の話のすじが分からない。
I cannot understand the gist of his story.
Here, 'すじ' is used to denote 'sinew' or 'stringy part' in the meat.
この肉はすじが多いね。
This meat has a lot of sinew.
In this sentence, 'すじ' is metaphorically representing 'principle' or 'core attribute' related to justice.