As far as Russian cases go, the prepositional case isn't all that bad. The noun endings are simple with next to no exceptions. Moreover the case is super common, which makes learning it very useful.
Let's take a look at one my favorite cases to learn in the Russian language!
The prepositional case is the only case in the Russian language that is always used with a preposition (hence the name).
Here are the three most common prepositions used with this case:
в (in, at)
in the car
in the room
in/at the university
на (on, at)
at the concert
on the table
at the lecture
When used with the prepositional case "о" in Russian corresponds to the English word about, as in thinking about something or talking about something.
about the concert
об этой книге*
about this book
*In this last example we use the alternate form of the preposition о: об. We use об before words that start with vowel sounds.
A Closer Look:
The differences between в and на
Noun endings in the prepositional case
Masculine noun endings
In the prepositional case masculine nouns will receive an added -е at the end of the word. Here's few examples:
Feminine and neuter noun endings
With feminine and neuter nouns the prepositional ending -е replaces the last vowel of the nominative form.
Notable exceptions (the -и ending)
There are two groups of nouns that receive a -и instead of the usual -е ending.
Feminine nouns ending in ь
The first group is feminine nouns that end in ь (soft sign). In this case we drop the soft sound and add -и in its place
Any noun ending in -ий, -ия, or -ие
No matter the gender, any noun ending in -ий, -ия, or -ие in the nominative will end with -и. In this instance the -и replaces the last vowel of the word.
That covers everything you'll need to get started with the prepositional case. Again, in my opinion, this is one of the easiest and most useful cases in Russian. Knowing how to use the prepositional case will go a long way toward increasing your ability in the language. Good luck!