a year ago, a year prior, year -on - year, year-over-year

Here’s how each expression is used, with examples and nuances:


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1. A year ago

Meaning: Exactly one year before now.

Usage: Simple past reference.

Example:
“I met her a year ago.”



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2. A year prior

Meaning: One year before a specific past event (not from now).

Usage: Often used in storytelling or reports.

Example:
“She moved to Seoul in 2022. A year prior, she had been living in Busan.”



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3. Year-on-year (UK) / Year-over-year (US)

Meaning: Used in business or statistics to compare data from one year to the same period in the previous year.

Usage: Often in financial or economic contexts.

Examples:

“Sales increased year-on-year.”

“There was a 10% year-over-year growth in revenue.”