[luxxi]

To add to freddie's explanation about polglasnik (semivowel). It is used in syllables that have no vowels in them. It's most often asociated with r.

e.g.
Prt (table cloth) has no vowel so we use this "polglasnik" it it.
or
Prstan (ring-the one you put on your finger) is divided into pr-stan. First syllable has no vowel so againt "polglasnik"