Smooth

光滑

guānghuá, guānghua

(lacking friction, not rough)

光滑

guānghuá

(mathematics, of a function: Having derivatives of all finite orders at all points within the function’s domain)

圓滑 /圆滑

yuánhuá

(suave; sophisticated)

平滑

pínghuá

(lacking friction, not rough)

平穩 /平稳

píngwěn

(without difficulty)

平靜 /平静

píngjìng

(placid, calm)

流暢 /流畅

liúchàng

(action: natural; unconstrained)

流暢 /流畅

liúchàng

(motion: unbroken)

自然

zìrán

(action: natural; unconstrained)

順利 /顺利

shùnlì

(without difficulty)