Prepositional plural (-ах / -ях, -ых / -их)

Nouns in the Prepositional Plural

We use the Prepositional case to talk about locations (в, на) and topics of conversation (о, об). Plural nouns take one of two endings:

• -ах for hard stems (форум → форумах, отзыв → отзывах).
• -ях for soft stems ending in -й, -ь, -е, or -ие (сеть → сетях, комментарий → комментариях, мнение → мнениях).

Adjectives in the Prepositional Plural

Good news: the Prepositional plural endings for adjectives and pronouns are identical to the Genitive plural endings:

• -ых for most hard-stem adjectives (новый → новых, социальный → социальных).
• -их for soft-stem adjectives, demonstrative pronouns (эти → этих), and stems ending in г, к, х, ж, ч, ш, щ due to spelling rules (хороший → хороших, плохой → плохих).

Let's put nouns and adjectives together to talk about sharing opinions online:

Notice how these endings attach to softer noun stems like сеть (network) and комментарий (comment):

Discussing Topics and Ideas

The preposition о (or об before vowels) always triggers the Prepositional case. You will use these plural forms frequently to discuss broad categories and shared interests.