Editing Serbo-Croatian (section)

=== Division by ''jat'' reflex ===
{{Main|yat}}

A series of [[isogloss]]es crosscuts the main dialects. The modern reflexes of the long [[Proto-Slavic language|Common Slavic]] vowel ''[[yat|jat]]'', usually transcribed *ě, vary by location as /i/, /e/, and /ije/ or /je/. Local varieties of the dialects are labeled Ikavian, Ekavian, and Ijekavian, respectively, depending on the reflex. The long and short ''jat'' is reflected as long or short */i/ and /e/ in Ikavian and Ekavian, but Ijekavian dialects introduce a ''ije''/''je'' alternation to retain a distinction.

Standard Croatian and Bosnian are based on Ijekavian, whereas Serbian uses both Ekavian and Ijekavian forms (Ijekavian for Bosnian Serbs, Ekavian for most of Serbia). Influence of standard language through state media and education has caused non-standard varieties to lose ground to the literary forms.

The jat-reflex rules are not without exception. For example, when short ''jat'' is preceded by ''r'', in most Ijekavian dialects developed into /re/ or, occasionally, /ri/. The prefix ''prě-'' ("trans-, over-") when long became ''pre-'' in eastern Ijekavian dialects but to ''prije-'' in western dialects; in Ikavian pronunciation, it also evolved into ''pre-'' or ''prije-'' due to potential ambiguity with ''pri-'' ("approach, come close to"). For verbs that had ''-ěti '' in their infinitive, the past participle ending ''-ěl'' evolved into ''-io'' in Ijekavian Neo-Štokavian.

The following are some examples:

{| class="wikitable"
|-
!English
!Predecessor
!Ekavian
!Ikavian
!Ijekavian
!Ijekavian development
|-
|beautiful
|*lěp
|lep
|lip
|lijep
| rowspan="2"| long ''ě'' → ''ije''
|-
|time
|*vrěme
|vreme
|vrime
|vrijeme
|-
|faith
|*věra
|vera
|vira
|vjera
|short ''ě'' → ''je''
|-
|crossing
|*prělaz
|prelaz
|prilaz
|prеlaz ''or''<br />prijelaz
|''pr'' + long ''ě'' → ''prije''<!--Does the /p/ really matter?-->
|-
|times
|*vrěmena
|vremena
|vrimena
|vremena
| rowspan="2"| ''r'' + short ''ě'' → ''re''
|-
|need
|*trěbati
|trebati
|tribat(i)
|trebati
|-
|heat
|*grějati
|grejati
|grijati
|grijati
|''r'' + short ''ě'' → ''ri''
|-
|saw
|*viděl
|video
|vidio
|vidio
|''ěl'' → ''io''
|-
|village
|*selo
|selo
|selo
|selo
|''e'' in root, not ''ě''
|}