res publica

NOUN /Rɛs_'publɪ,kɑ/
11 LETTERS · 3 SYLLABLES · STARTS WITH R

res publica is a valid 11-letter word worth 16 points in Scrabble and 21 points in Words with Friends.

SCRABBLE WORDS WITH FRIENDS
R1E1S1P3U1B3L1I1C3A1
1 + 1 + 1 + 0 + 3 + 1 + 3 + 1 + 1 + 3 + 1 =16 PTS
DOUBLE WORD → 32TRIPLE WORD → 48
MEANING

What does res publica mean?