The next endings are the 3rd declension. (It wasn't mentioned before that the blocks in the blue table below are called declensions. For example, the 1st declension is the -as, -ias, -is and -ys endings.)

The 3rd declension is very common. At first it may be hard to distinguish its nouns from nouns that start with -is (brolis, Laimis, rašiklis, etc), because they also have -is in the nominative case. You will have to memorize which endings a word takes.

Let's see two examples:

vagis (thief)
vagies
vagiui
vagį
vagimi
vagyje
vagie!

vagys (thieves)
vagių
vagims
vagis
vagimis
vagyse
vagys!


rūšis (kind)
rūšies
rūšiai
rūšį
rūšimi
rūšyje
rūšie!

rūšys (kinds)
rūšių
rūšims
rūšis
rūšimis
rūšyse
rūšys!


Vagis is a masculine word, so it has an iui ending in singular dative case. Feminine words (like rūšis) takes the ending iai.

Tas greitas vagis bėga namo! That quick thief is running home!
Yra tik viena kačių rūšis! There is only one kind of cats!

Du vagys važiuoja autobusu per tiltą. Two thieves are driving on a bus across a bridge.
Aš rašau apie penkias automobilių rūšis. I am writing about five kinds of cars.