Esperanto edit

Esperanto numbers (edit)
300
 ←  20  ←  29 30 31  →  40  → 
3
    Cardinal: tridek
    Ordinal: trideka

Etymology edit

From tridek +‎ -a.

Adjective edit

trideka (accusative singular tridekan, plural tridekaj, accusative plural tridekajn)

  1. (ordinal number) thirtieth