不是 + A + 而是 + B
而是 (érshì) is used to express "but rather" or "but instead," typically following a negation with 不是. Together, the pattern 不是…而是… means "it is not…but rather…," allowing the speaker to correct a misconception or clarify the true situation.
我喜欢的不是颜色,而是款式。
wǒ xǐhuan de bù shì yánsè, ér shì kuǎnshì.
What I like is not the color, but the style.
他不是不想帮忙,而是真的没有时间。
Tā bú shì bù xiǎng bāngmáng, ér shì zhēn de méiyǒu shíjiān.
It's not that he doesn't want to help, but that he really doesn't have time.
成功靠的不是运气,而是努力。
Chénggōng kào de bú shì yùnqì, ér shì nǔlì.
Success depends not on luck, but on hard work.