-ный

Etymology
.

Suffix

 * 1) -ish, -ic, -al, -ed;

Usage notes
Note the following properties:
 * A velar (as well as ц) normally turns into a palatal as a result of the . This and the following several properties are due to the *ь that was formerly present at the beginning of the suffix.
 * A stem ending in -л turns into -ль before the suffix; contrariwise, all other stems ending in -ь lose this.
 * With reducible nouns, the stem assumes its non-reduced form before the suffix. With feminine and neuter nouns, this form is found only in the genitive plural. This applies even to nouns with no plural.
 * ё may turn back into е before the suffix.
 * The stress is sometimes (but not always) drawn onto the preceding syllable.
 * Foreign nouns ending in invariant -е change this to stressed -е́й before the suffix.
 * Some adjectives in -ия, -ие change this to stressed -е́й before the suffix (as if they ended in -ья, -ье/-ьё).
 * But some adjectives in -ия, -ие have the expected change to -и́й:
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * ё may turn back into е before the suffix.
 * The stress is sometimes (but not always) drawn onto the preceding syllable.
 * Foreign nouns ending in invariant -е change this to stressed -е́й before the suffix.
 * Some adjectives in -ия, -ие change this to stressed -е́й before the suffix (as if they ended in -ья, -ье/-ьё).
 * But some adjectives in -ия, -ие have the expected change to -и́й:
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * The stress is sometimes (but not always) drawn onto the preceding syllable.
 * Foreign nouns ending in invariant -е change this to stressed -е́й before the suffix.
 * Some adjectives in -ия, -ие change this to stressed -е́й before the suffix (as if they ended in -ья, -ье/-ьё).
 * But some adjectives in -ия, -ие have the expected change to -и́й:
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * Some adjectives in -ия, -ие change this to stressed -е́й before the suffix (as if they ended in -ья, -ье/-ьё).
 * But some adjectives in -ия, -ие have the expected change to -и́й:
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * But some adjectives in -ия, -ие have the expected change to -и́й:
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).
 * Adjectives in -ный may be formed directly from foreign nouns or adjectives, as in and  (there is no such adjective *молекуля́р and no such noun *кассацио́н).

Note in particular that nouns in, have corresponding adjectives in unstressed -очный.