apparently right but actually wrong; specious (idiom)
Definitions (粵典–words.hk)
語句
表面似係咁，實際上唔係 correct in appearance but in fact not
Definitions (Wiktionary)
phrase, idiomatic
seemingly so, but not really; appears right, but in fact wrong; specious
這些話，講起來好像有道理，實際上是毫無根據、似是而非的空談。
这些话，讲起来好像有道理，实际上是毫无根据、似是而非的空谈。
zhè xiē huà ， jiǎng qǐ lai hǎo xiàng yǒu dào lǐ ， shí jì shàng shì háo wú gēn jù ， sì shì ér fēi de kōng tán ． Such remarks, however plausible, are actually groundless and specious empty talk.
Definitions (Kaifangcidian)
（沒有對應漢語詞彙）
Definitions (HSK3.0)
HSK3 七一九级词汇表 #3924
Examples (粵典–words.hk)
Cantonese
似是而非
似是而非
ci5 si6 ji4 fei1
correct in appearance but in fact not
Examples (Wiktionary)
Mandarin
这些话，讲起来好像有道理，实际上是毫无根据、似是而非的空谈。
這些話，講起來好像有道理，實際上是毫無根據、似是而非的空談。
zhè xiē huà ， jiǎng qǐ lai hǎo xiàng yǒu dào lǐ ， shí jì shàng shì háo wú gēn jù ， sì shì ér fēi de kōng tán ．
Such remarks, however plausible, are actually groundless and specious empty talk.