Question: It's time to propose the topics for our Challenge Week!

Some notes:

1. Propose one topic per answer (make it CW by checking the checkbox under your answer);

Write them like  

`## Topic <br><br>  

"description"`.
2. No maximum of proposals, but don't just propose tons of stuff. Propose things that could stimulate questions and answers.
3. Vote other proposals **up** if you like them, and **down** if you don't.
4. Include a short description or notes, otherwise the system won't let you post your answer.

For each Challenge Week, we'll take the most voted proposal (excluding the already asked ones), so keep proposing! Don't wait for others to propose!

Any questions? Use the comments below. :)

Answer: 
Historical linguistics
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The study of how languages evolve over the centuries usually interests not only professional linguists, but also classicists, literary critics, as well as other users just interested in languages in general. Historical linguistics will probably make for a great challenge!
Phonology
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The branch of linguistics which investigates the ways in which sounds are used systematically in different languages to form words and utterances.