line; spoken line
Refers to a character's spoken line in a play, film, TV show, comic, etc. Often used in the plural sense of 'one's lines'.
He forgot his lines on stage.
The lines in this movie are very memorable.
Used for something someone says, often with a nuance of being a notable or characteristic remark. Can be used in everyday conversation.
I'm always surprised by the things he says.
That's not like you to say something like that.
stock phrase; cliché; platitude
Refers to a predictable or overused phrase, often with a negative or ironic nuance. Common in expressions like お決まりのセリフ (the usual line).
He was fed up with hearing that same old line again.
I've gotten used to politicians' stock phrases.
He delivered his lines while feeling nervous.
"I'm busy today" is his usual line.
The new actor memorizes his lines every night.
I got nervous and stumbled over my lines.
発言 is a formal term for a statement or remark someone makes, while セリフ specifically refers to a line of dialogue or a characteristic remark, often in a script or conversation.
文句 often implies a complaint or set phrase with a negative tone, whereas セリフ in its 'stock phrase' sense (お決まりのセリフ) is more neutral or ironic, referring to a predictable line.
The most common spelling in modern Japanese; usually written in kana.
Kanji spelling; the reading せりふ is a jukujikun. The alternative reading だいし is rare and not used in modern Japanese.
Hiragana spelling, also common.
Rarely used kanji form.
Originally a theatrical term. The kanji 台詞 is a jukujikun reading, combining 台 (platform, stand) and 詞 (words, lyrics). The reading せりふ is thought to derive from 迫り (seri, a stage lift) + 言ふ (iu, to say), referring to lines spoken on the raised stage. The katakana spelling セリフ is now standard.