She had to remind him once again to take out the trash.
once in a lifetime
Frequency:
70
%
Visiting Paris is a once in a lifetime experience.
once in a while
Frequency:
65
%
I like to treat myself to ice cream once in a while.
Idiomatic Expressions for once
Phrase: once in a lifetime
Meaning: a rare or unique opportunity that may not happen again
Usage: Visiting the Grand Canyon is a once in a lifetime experience.