# -о-
## Bulgarian
### Alternative forms

* -е- (-e-)

### Etymology

For native terms, inherited from Old Church Slavonic -о- (-o-), from Proto-Slavic *-o-.
For borrowings, from Latin -o- or Ancient Greek -ο- (-o-).

### Interfix

-о- • (-o-)
* Used to form compound words. Usually excrescent.

#### Derived terms
### References

* Тодор Бояджиев, Иван Куцаров, Йордан Пенчев (1999) “3. Морфемен състав на производната дума [3. Morphemic structure of words]”, in Тодор Бояджиев, editor, Съвременен български език [Contemporary Bulgarian Language] (in Bulgarian) (textbook), Sofia, Bulgaria: ИК "Петър Берон", →ISBN, pages 240, 241

## Macedonian
### Etymology

Inherited from Old Church Slavonic -о- (-o-), from Proto-Slavic *-o-.

### Pronunciation

* IPA: [ɔ]

### Interfix

-о- • (-o-)
* Interfix used to form compound nouns and adjectives.

#### Derived terms
## Moksha
### Pronunciation

* IPA: /ə/

### Interfix

-о- • (-o-)
* an interfix that surfaces before various suffixes, after a hard consonant

#### See also

* -е- (-e-) (after soft consonants)

## Russian
### Alternative forms

* -е- (-e-) — used after soft consonants, hushing consonants (ш ж ч щ) and ц

### Etymology

Inherited from Old East Slavic -о- (-o-), from Proto-Slavic *-o-.

### Pronunciation

* IPA: [ə]

### Interfix

-о- • (-o-)
* Interfix used to form compound nouns and adjectives.
    ‎челове́к (čelovék, “human”) + ‎-о- (-o-) + ‎ненави́стник (nenavístnik, “hater”) → ‎человеконенави́стник (čelovekonenavístnik, “misanthrope”)
    ‎а́том (átom, “atom”) + ‎-о- (-o-) + ‎ходи́ть (xodítʹ, “to go, to walk”) → ‎атомохо́д (atomoxód, “atomic-powered vessel”)
    ‎круг (krug, “circle”) + ‎-о- (-o-) + ‎верте́ть (vertétʹ, “to twist, to turn”) → ‎кругове́рть (krugovértʹ, “whirlwind”)
    ‎бе́лый (bélyj, “white”) + ‎-о- (-o-) + ‎снег (sneg, “snow”) + ‎-ный (-nyj) → ‎белосне́жный (belosnéžnyj, “snow-white”)
    ‎пе́рвый (pérvyj, “first”) + ‎-о- (-o-) + ‎очередно́й (očerednój, “foremost”) + ‎-ной (-noj) → ‎первоочередно́й (pervoočerednój, “first and foremost”)
    ‎пе́ший (péšij, “unmounted, on foot”) + ‎-е- (-e-) + ‎ходи́ть (xodítʹ, “to go, to walk”) → ‎пешехо́д (pešexód, “pedestrian”)
    ‎ни́щий (níščij, “poor, destitute”) + ‎-е- (-e-) + ‎броди́ть (brodítʹ, “to wander, to roam”) → ‎нищебро́д (niščebród, “beggar, tramp (colloquial, dated); cheapskate (pejorative)”)
    ‎верте́ть (vertétʹ, “to twist, to turn”) + ‎-о- (-o-) + ‎лете́ть (letétʹ, “to fly”) → ‎вертолёт (vertoljót, “helicopter”)

#### Usage notes

* The first part of the compound is normally a noun or adjective, but sometimes a verb. In all cases its ending, back to the final consonant of the stem.
* The second part of the compound is frequently a verb, in which case it also loses its ending, back to the final consonant of the stem, which is normally made hard if it is a paired soft consonant, with е becoming ё in the process, as in вертолёт (vertoljót, “helicopter”) and атомохо́д (atomoxód, “atomic-powered vessel”) (but see also кругове́рть (krugovértʹ, “whirlwind”), where the final consonant remains soft). Compare similarly formed Latinate compounds such as aqueduct.
* The interfix itself is never stressed, but the word preceding the interfix may in some cases have a secondary stress. If the stress of that word is on the stem, the secondary stress will generally be on the same syllable, but if the stress was on the lost ending, the last syllable of the stem will bear the secondary stress, e.g. бронеавтомоби́ль (broneavtomobílʹ) (stressed as бро̀неавтомоби́ль), from броня́ (bronjá) + автомоби́ль (avtomobílʹ).

#### See also

* -и- (-i-) (less common interfix sometimes found when the first component is a verb or cardinal number)

## Serbo-Croatian
### Etymology

Inherited from Proto-Slavic *-o-.

### Interfix

-о- (Latin spelling -o-)
* Interfix used for forming nominal compounds.
    киш + -о- + -бран → ки̏шобра̄н

## Ukrainian
### Etymology

Inherited from Old Ruthenian -о- (-o-), from Old East Slavic -о- (-o-), from Proto-Slavic *-o-.

### Interfix

-о- • (-o-)
* Used to form compounds.