Doubling softens: đo đỏ, xanh xanh (-ish)

Say a one-syllable adjective twice and it becomes softer, like English "-ish": xanh xanh (bluish, greenish), vàng vàng (yellowish), buồn buồn (a bit down), nho nhỏ (smallish, small and cosy).

The first copy often changes a little. If the word has a tone mark above it, the first copy usually loses it: đỏ gives đo đỏ (reddish), tím gives tim tím (purplish), trắng gives trăng trắng (whitish). If it has the dot below, the first copy takes the falling mark instead: nhẹ gives nhè nhẹ (gently), mặn gives mằn mặn (a little salty). And a final p, t or c becomes m, n or ng: mát gives man mát (pleasantly cool), đẹp gives đèm đẹp (quite pretty). At first, just learn to recognise them.

They're common for colours, tastes and the weather, and they sound gentle: Trời man mát. It's nice and cool.

Not every double softens. Many two-part words, like vui vẻ (cheerful) and sạch sẽ (clean and tidy), are simply ordinary words. Longer doubles that make something stronger have their own page, and so do rhyming pairs like cây cối (trees, plants), which name a whole group.