[Do you know?]
Both "久" and "长" means a long time. Is there any difference between them?
久 (jiǔ): long time
长 (chánɡ): long distance; length; strong point; be good at
"长" is polysemous. "长" and "久" mean the same when refering to time. Except that, they cannot be exchanged in other cases.
√ 我久久不能忘记你。(wǒ jiǔ jiǔ bù nénɡ wànɡ jì nǐ.)
I still couldn't forget you after a long time.
√ 长江全长6300多公里。(chánɡ jiānɡ quán chánɡ 6300 duō ɡōnɡ lǐ.)
The Yangtze River is more than 6,300m long.
Please visit Chinlingo