Uncountable Nouns That Start with O and End with O

Explore 14 verified English uncountable nouns that start and end with O, including Oregano, Otto, Orzo, Ortho, Ouzo, Oleo and Outgo. Sort these mass nouns and non-count terms for substances and concepts by word length for quantifier accuracy, academic writing, and ESL study below, or check quantifier and measurement rules in our noun grammar guide.