大 + Adjective/Verb
大 (dà) can function as an adverb meaning "greatly" or "very much," intensifying the degree of a following adjective or verb. In this usage it emphasizes a large difference or extent. For example, 大不相同 means "greatly different."
今年的天气和去年大不一样。
Jīnnián de tiānqì hé qùnián dà bù yīyàng.
This year's weather is very different from last year's.
这次改版之后,效果大有改善。
Zhè cì gǎibǎn zhīhòu, xiàoguǒ dà yǒu gǎishàn.
After this revision, the results have greatly improved.
他的态度大为改变,让人很惊讶。
Tā de tàidù dà wéi gǎibiàn, ràng rén hěn jīngyà.
His attitude changed dramatically, which surprised everyone.