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(spoken) line (in a play, film, comic, etc.); one's lines
comment; remark; phrase; words
stock phrase; set phrase; cliché; platitude
「科白」 has another reading with different meanings.
彼女は科白を完璧に暗記していた。
She had memorized her lines perfectly.
映画の有名な科白を真似してみた。
I tried imitating a famous line from the movie.
舞台の科白を何度も練習した。
I practiced the stage lines over and over.