Extension and Extra

Extension noun - The act of making longer.

Extra and extension are semantically related In some cases you can use "Extra" instead a noun "Extension".

Nearby Words: extend, extended, extent, extensive, extensively

Extra noun - An interchangeable part or piece of equipment that is kept on hand for replacement of an original.

Extension and extra are semantically related in addition topic. Sometimes you can use "Extension" instead a noun "Extra", if it concerns topics such as accessory.