Three- and four-syllable doubles intensify: vội vội vàng vàng

Doubling can make a word stronger and more vivid. Three patterns are worth knowing.

A two-syllable word AB can become A A B B: vội vàng (hurried) becomes vội vội vàng vàng, rushing about in a real hurry. Another four-syllable pattern repeats the first syllable with -a or a similar vowel in the middle: lúng túng (flustered) becomes lúng ta lúng túng, and hớt hải becomes hớt ha hớt hải (in a frantic rush).

Some words grow to three syllables: sạch (clean) becomes sạch sành sanh, completely gone, not a crumb left, and dửng dưng (indifferent) becomes dửng dừng dưng. These are fixed and fairly few, so learn them as you meet them.

Sound words double to show a sound that keeps going: mưa ào ào (rain pouring down), xe chạy ầm ầm (traffic roaring past), gõ cửa cộc cộc (knocking on the door).

All of these belong to lively speech and storytelling, and to descriptive writing in features and fiction. They paint a picture, often with some exaggeration, so they don't fit in a report. You can't invent new ones freely; use the ones you've heard.

Two-syllable doubling of an adjective, like đo đỏ (reddish), does the opposite: it softens.