Used as a prefix in loanword compounds to mean 'first', 'best', or 'primary', e.g., プライムタイム (prime time), プライムレート (prime rate).
Programs broadcast during prime time have high ratings.
When the prime rate goes up, mortgage interest rates also rise.
prime symbol (')
Refers to the typographical symbol (') used in mathematics, measurements, or as a diacritic; not a common standalone noun in everyday Japanese.
In mathematics, the prime symbol is used to denote differentiation.
prime time; peak TV viewing hours
prime lending rate; prime rate
prime minister
Borrowed from English 'prime'.