Mirror words

Mirror words are unintentional repetitions of a word or its root close enough together that a reader notices the writing instead of the scene — the accidental echo a line edit exists to catch.

An example, with the echo left in:

Struggling to collect his thoughts, Friedrich just obeyed. His muscles felt like they hadn't been used in months, and every move took focused thought, but he finally shoved himself into the opening between the cars.

Thoughts in the first clause, thought two lines later. Neither use is wrong, and the sentence is grammatical throughout, but the second one chimes against the first and the reader hears the repetition rather than the man hauling himself between railway carriages. Change one — every move took concentration — and the passage goes quiet again.

The echo does not have to be exact to register. Shared roots do it, and so does sound: accidental alliteration like clean cut clothes trips the eye for the same reason. Deliberate repetition is a different matter entirely — it is one of the strongest tools in prose — which is why the test is intent, not frequency.

They are difficult to catch by reading silently, because the eye supplies what it expects. Reading aloud finds them, and so does a search for any noticeable word in the paragraphs on either side. A line edit hunts them by default; a copy edit will not, because nothing here is incorrect.