adverb
    
    one time only
    
    
    
    
    
    
    
    
    
    
    
    
    
    at any one time :ever
    
    
    
    
    
    at some time in the past
    
    
    
    
    
    
    
    
    
    
    
    
    
    once again/more
    
    for another time :one more time :again
    
    
    
    
    
    
    
    once and for all
    
    now and for the last time
    
    
    
    
    
    
    
    
    
    once bitten, twice shy
    
    
    
    once in a blue moon
    
    see blue moon
    
    once in a while
    
    sometimes but not often :occasionally
    
    
    
    
    
    once upon a time
    
    at some time in the past
    
    
    
    Once upon a time is the traditional way to begin a fairy tale.
    
    
    
    noun
    
    [noncount] :one single time
    
    
    
    
    
    
    
    at once
    
    at the same time
    
    
    
    
    
    
    
    right away :without delay :immediately
    
    
    
    
    
    conjunction
    
    at the moment when :as soon as