Learn English – Are “Arc” and “Arch” interchangeable

word-difference

I've checked the dictionaries and both words have a common meaning:

arc – a shape or structure resembling an arc.

arch – a curved symmetrical structure spanning an opening and typically supporting the weight of a bridge, roof, or wall above it.

Can both these words be interchangeable?

  • We went through the arc.
  • We went through the arch.

Best Answer

Here is the Oxford Dictionary definition for arc that you referred to:

arc noun

1A part of a curve, especially a part of the circumference of a circle:
the point where a tangential line touches the arc of a circle

1.1 A shape or structure resembling an arc:
the huge arc of the sky

Note that, although definition 1.1 refers to a structure, the word arc in the following example (and in all of the other examples quoted) if followed by of. arc is not an actual structure: it serves only to define the shape of the real structure (the sky).

The definition in the Oxford dictionary would be better written as

the shape of a structure resembling an arc.

Here are the definitions from the Cambridge dictionary: as you can see, there is no (STRUCTURE) meaning for arc.

arc
noun [ C ] (CURVE) the shape of part of a circle, or other curved line.

arch
noun [ C ] (CURVED STRUCTURE) a structure, consisting of a curved top on two supports, that holds the weight of something above it.
noun [ C ] (SHAPE) something that has the shape of an arch, often used for decoration:

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