<p>I would call them <em>stutter-free</em> words, since there is the notion of <em>stutter-invariant language</em>, which is already well-known.</p>

CC BY-SA 4.0
2022-03-08T18:45:32.590Z
2022-03-09T02:38:30.743Z
2022-03-09T02:38:30.743Z
J.-E. Pin
<p>Is there a common name in combinatorics for words that do not have square of size 1 ? That is words such that no symbols appears twice in a row or, more formally, words <em>not</em> in <span class="math-container">$\bigcup_{s\in\Sigma} \Sigma^* s s \Sigma^*$</span> where <span class="math-container">$\Sigma$</span> is our alphabet.</p>

CC BY-SA 4.0
2022-01-31T17:38:04.033Z
I propose calling the occurrence of a repeated letter a “hiccup” and correspondingly calling your language hiccup-free.
Aryeh
<reference-request><fl.formal-languages><combinatorics>
Name for words without squared symbols
Johan
# Name for words without squared symbols

(Asked by: username_0 on 2022-01-18)

Is there a common name in combinatorics for words that do not have square of size 1 ? That is words such that no symbols appears twice in a row or, more formally, words *not* in $\bigcup\_{s\in\Sigma} \Sigma^\* s s \Sigma^\*$ where $\Sigma$ is our alphabet.

**Tags:** reference-request, fl.formal-languages, combinatorics
> **Comments:**
> **username_1**: I propose calling the occurrence of a repeated letter a “hiccup” and correspondingly calling your language hiccup-free.  

---

## 1 answers

### Answer by username_2 on 2022-03-08. Score: 8 | Accepted answer

I would call them *stutter-free* words, since there is the notion of *stutter-invariant language*, which is already well-known.


---

