Most masculine nouns end in a consonant.  Consonants may be 'hard' or less frequently 'soft'.  The 'soft' consonants are c, ć, č, dž, đ, j, lj, nj, š, ž; all other consonants are hard.

ćovjek      (hard)
vlak          (hard)
prijatelj    (soft) friend

Some masculine nouns end in -o (or -e after a 'soft' consonant).  This is the case with a large number of proper names, eg, Marko, Ivo and a number of nouns which used to end in -l. This l occurs in other cases.

          ugao 'corner'  -  u uglu  'on the table'
but    sto in Serbian - na stolu 'on the table

Masculine nominative plural ending: -i .  Most monosyllabic masculine nouns have an additional syllable in the plural:

sto          stolovi
vlak        vlakovi

If the final consonant is soft, then -ovi becomes -evi;

muz        muzevi (husband)

Certain combinations of consonants and vowels involve consonant changes, for example the combination k + l is replaced by -ci.

putnik     putnici

There are a number of masculine nouns ending in -a: vođa (leader), sluga (servant), pristaša (follower), pijanica (drunkard), propalica (good-for-nothing), Nikola (Nicholas), Jura (George), , etc