Onus
O
offeroperate
omlet
it begins with the letter o. but if you are french, it begins with a letter o.
I believe you're looking for the word ode.
outdoors
Overcast and ocean breeze are weather words. They begin with the letter o.
There are no such words in the English language.
Obliteration and oblivion are synonyms for death. They begin with the letter o.
Opportunity or own decision. Those words mean freedom and begin with O.
a, because it doesn't begin with a,e,i,o,u