Serbo-Croatian
Pitch accent

Apart from Slovene, Serbo-Croatian is the only Slavic language with a pitch accent (simple tone) system. This feature is present in some other Indo-European languages, such as Norwegian, Ancient Greek, and Punjabi. Neo-Shtokavian Serbo-Croatian, which is used as the basis for standard Bosnian, Croatian, Montenegrin, and Serbian, has four "accents", which involve either a rising or falling tone on either long or short vowels, with optional post-tonic lengths:

The tone stressed vowels can be approximated in English with set vs. setting? said in isolation for a short tonic e, or leave vs. leaving? for a long tonic i, due to the prosody of final stressed syllables in English.

General accent rules in the standard language:

There are no other rules for accent placement, thus the accent of every word must be learned individually; furthermore, in inflection, accent shifts are common, both in type and position (the so-called " mobile paradigms "). The second rule is not strictly obeyed, especially in borrowed words.

Comparative and historical linguistics offers some clues for memorising the accent position: If one compares many standard Serbo-Croatian words to e.g. cognate Russian words, the accent in the Serbo-Croatian word will be one syllable before the one in the Russian word, with the rising tone. Historically, the rising tone appeared when the place of the accent shifted to the preceding syllable (the so-called "Neo-Shtokavian retraction"), but the quality of this new accent was different – its melody still "gravitated" towards the original syllable. Most Shtokavian (Neo-Shtokavian) dialects underwent this shift, but Chakavian, Kajkavian and the Old-Shtokavian dialects did not.

Accent diacritics are not used in the ordinary orthography, but only in the linguistic or language-learning literature (e.g. dictionaries, orthography and grammar books). However, there are very few minimal pairs where an error in accent can lead to misunderstanding.
oulipo:avoid_letter[a]