Her smile expressed her thanks.
- Son sourire exprimait sa gratitude.
I like the way you smile.
- J'aime ta façon de sourire.
He grinned with delight.
- Il fit un large sourire de satisfaction.
That person has had an odd grin on his face for a while. What do you suppose is behind it?
- Cette personne a eu un étrange sourire sur la figure pendant un instant. Que pensez-vous que cela cache ?
She always talks with a smile on her lips.
- Elle parle toujours le sourire aux lèvres.
She looked at him with a smile on her face.
- Elle le regarda, le sourire aux lèvres.