-енний

Borrowed from Old Church Slavonic -еньнъ (-enĭnŭ), from енъ (enŭ) + ьнъ (ĭnŭ). Originally used to form adjectives from past passive participles in Old Church Slavonic, later reinterpreted as a past passive participle suffix within the Russian literary language. Compare the native past participle suffix -ячий (-jačyj), which developed into an adjective suffix. Reanalize as -ен (-en) +‎ -ний (-nyj)

• -єнний (-jennyj)

• IPA^(key): [ enːei̯]

-енний • (-ennyj) m (feminine -енна)

1. used to form past passive participles from verbs in -ити (-yty) and -ати (-aty), which are frequently lexicalized into adjectives

   ‎проща́ти (proščáty, “to forgive”) + ‎-енний (-ennyj) → ‎непроще́нний (neproščénnyj, “unforgiven, unforgivable”)

• As a means of forming past passive participles, the suffix as written occurs mostly stressed. Generally, this suffix occurs with accent-a verbs (stem-stressed verbs ending in unstressed -ити (-yty) and -ати (-aty)) and accent-c verbs (ending-stressed verbs in -и́ти (-ýty) and -а́ти (-áty), where the present and synthetic future tense, except for the first person singular, are stem-stressed, for example води́ти (vodýty) with present tense воджу́ (vodžú), во́диш (vódyš), во́дить (vódytʹ), etc.). It does normally occur with accent-b verbs (ending-stressed verbs where the entire present and synthetic future tense is ending-stressed, for example вини́ти (vynýty) with present tense виню́ (vynjú), вини́ш (vynýš), вини́ть (vynýtʹ), etc.), which use -е́нний (-énnyj). However, there are exceptions in both directions, e.g. accent-c діли́ти (dilýty) (present tense ділю́ (diljú), ді́лиш (dílyš)) with past passive participle неподіле́нний (nepodilénnyj) and accent-b викроїти (vykrojity) (present tense викро́юю (vykrójuju), викро́юєш (vykrójuješ)) with past passive participle невикрої́нний (nevykrojínnyj).
• This suffix triggers iotation (unlike the homophonous adjective-forming suffix below).

• -анний (-annyj)
• -нний (-nnyj)

• -тий (-tyj)

• -енний: IPA^(key): [ enːei̯]
• -е́нний: IPA^(key): [ ˈɛnːei̯]

-енний • (-ennyj) m (feminine -енна)

1. used to form adjectives from nouns, with the meaning "having the property of X"

• This suffix triggers the Slavic first palatalization of velars, but does not trigger iotation (unlike the homophonous past-participle-forming suffix above).
• In the colloquial meaning "very X", the suffix is normally stressed, while in the meaning "having the property of X" it is normally unstressed.