沿う and 横切る: following a river and crossing a road
Compare a path running along a river with a cat crossing a road to identify following along a reference feature and moving across it.
Identify the reference feature for 沿う
沿う (そう) here describes following along a reference feature. First, identify the relationship between the river and the path.
“川に沿って続く細い道を歩いた。” says that the speaker walked along a narrow path following the river. 川に沿って続く describes the path; that narrow path is what the person walked along.
Identify what is crossed in 横切る
横切る (よこぎる) means moving across something. Distinguish the moving subject from the object being crossed.
“猫が静かな道を素早く横切った。” says that a cat quickly crossed the quiet road. The cat is moving, the road is crossed, and 素早く preserves the manner of movement.
Distinguish the route’s relation to the reference feature
In the first example, the river is the feature that the path follows; in the second, the road is what the cat crosses. Following a feature and crossing it express different relationships.
沿う does not always define a geometrically parallel straight line. Read following the river and crossing the road without adding angles or a comparison of shortcut lengths.
Does walking on a path that runs 沿って the river mean crossing the river with 横切る?
Show the answer and why
No. The river is the reference feature followed by the path, and the person walked along that path. In the separate cat example, the road itself is the object crossed.