Through, Over, and Under
Through for enclosed 3D spaces, over for arcing above an obstacle, under for passing beneath — and how to tell them apart from across and above.
Through, Over, and Under: 3D Spaces and Obstacles
This group produces some of the most persistent preposition errors at B1–B2 level. Longman corpus research identifies 'across' incorrectly substituted for 'through' in enclosed-space contexts in approximately one-third of error instances involving these two prepositions. The root cause: learners apply the 'one side to the other' logic of 'across' to tunnels, forests, and caves — failing to activate the three-dimensionality test.
Through — Moving Inside a 3D Enclosed Space
Use through when you move inside a space that encloses you — entering at one end and exiting at the other:
The river flows through the city centre before reaching the sea.
The cat squeezed through the gap in the fence.
Over — Arcing Above an Obstacle
Use over when movement describes an arc above something, going up one side and down the other:
The children climbed over the tall wooden fence to get their ball back.
The plane flew over the mountains.
Under — Passing Beneath a Structure
The cat squeezed under the gate.
The Through/Across Decision Rule
Ask: Am I inside the space while moving? If yes, use through. A bridge is a flat surface you walk on top of → across. A tunnel encloses you inside → through. A forest surrounds you on all sides → through. An open field is flat → across.
Common Mistakes
✗ She swam across the underwater cave. → ✓ She swam through the underwater cave.
✗ The cat squeezed through the fence. → ✓ The cat squeezed through the gap in the fence. (you need an opening)
✗ The horse jumped through the hedge. → ✓ The horse jumped over the hedge.