赶快 (gǎn kuài) is an adverb meaning 'hurry up' or 'quickly'—it conveys urgency and the need to act without delay. The character 赶 (gǎn) originally means 'to chase', 'to rush', or 'to catch up', while 快 (kuài) means 'fast' or 'quick'. Together, they intensify the sense of speed and immediacy, making 赶快 stronger and more colloquial than just 快 alone. It’s commonly used in spoken Mandarin and informal writing, especially when urging someone to move faster or complete a task promptly.

This word typically appears at the beginning of a sentence or before a verb—for example, '赶快走！' (Hurry up and go!)—and can also follow subject pronouns like 你 or 我. It’s not used attributively (e.g., you wouldn’t say *赶快的车); it always modifies verbs or entire clauses. While it expresses urgency, it’s neutral in tone—not inherently rude—but context and intonation determine politeness.