Something ordinary is something that happens every day. Maybe you should skip your ordinary breakfast and try something new.
Although we often use the adjective ordinary to mean "ho-hum, nothing special," it actually comes from the Latin root for "rule." You could think of ordinary things as almost like rules in your life. As a noun it has other meanings. In heraldry (that's the art of the family shield), an ordinary is a conventional figure. A probate judge is called an ordinary, as is the clergyman who prepares prisoners for death.