(=definitely)
[seem, appear] certainement
→ whatever it is, it certainly seems to work
→ If nothing is done there will certainly be an economic crisis.
[think, expect]
vraiment
I certainly expected something better. Je m'attendais vraiment à quelque chose de mieux.
So it was a surprise? -- It certainly was! C'était donc une surprise? -- Ça oui alors!
certainly not! certainement pas!
it's certainly true that ... il ne fait aucun doute que ...