而 / 然而: whereas, but, however
【四20】【四49】连词 / conjunctions
Tone colorsā tone 1á tone 2ǎ tone 3à tone 4a neutral
而 sets two different subjects or facts side by side, like "whereas" or "while": 来借书的人少了，而来学习的人多了。 Each half has its own topic, and the contrast is real. It belongs to writing and careful speech; in everyday talk, 但是 or 可是 is enough.
然而 is a formal "yet, however" that opens the second clause and marks the turnaround: 我知道运动对身体好，然而我总是没有时间。 Stronger and more written than 但是 / 可是, it goes before the subject (the adverb 却, by contrast, follows the subject).
Watch out: 而 does not join two nouns (for "and" between nouns, say 和), and it wants two truly opposed topics. Compare 而是 ("but rather"), 反而 ("on the contrary") and 却 ("yet", after the subject).
Examples
北方冬天常常下雪，而南方常常下雨。
Běifāng dōngtiān chángcháng xià xuě, ér nánfāng chángcháng xià yǔ.In winter it often snows in the north, whereas in the south it often rains.
姐姐爱看书，而弟弟爱运动。
Jiějie ài kàn shū, ér dìdi ài yùndòng.My older sister loves reading, whereas my younger brother loves sport.
来借书的人少了，而来学习的人多了。
Lái jiè shū de rén shǎo le, ér lái xuéxí de rén duō le.Fewer people come to borrow books, while more come to study.
我知道每天运动对身体好，然而我总是没有时间。
Wǒ zhīdào měi tiān yùndòng duì shēntǐ hǎo, ránér wǒ zǒngshì méiyǒu shíjiān.I know exercising every day is good for you, yet I never have the time.
他们找了很久，然而什么也没找到。
Tāmen zhǎo le hěn jiǔ, ránér shénme yě méi zhǎodào.They searched for a long time, but found nothing.
手机上的书又多又方便，然而还有很多人喜欢翻纸质书。
Shǒujī shang de shū yòu duō yòu fāngbiàn, ránér hái yǒu hěn duō rén xǐhuan fān zhǐzhì shū.Books on a phone are plentiful and convenient, yet many people still like to leaf through paper books.
Common mistakes
✗ 我喜欢苹果而香蕉。 → ✓ 我喜欢苹果和香蕉。 (而 does not join nouns, 和 says "and").
✗ 我很累，而我睡不着。 → ✓ 我很累，但是睡不着。 (而 needs two subjects or topics in opposition, not one subject with a surprise).
✗ 他很聪明，他然而很懒。 → ✓ 他很聪明，然而他很懒。 (然而 comes before the subject).