| must | dever | ||
| I must | eu dev | o | |
| you/he/she must | você/ele/ela dev | e |
DEVER usually gets combined with another verb immediately following it to form powerful expressions.
dever + ser Ela deve sera apaixonada. She must be in love.
dever + ir Você deve ir. You should go.
dever + ter Deve ter sido amor. Must have been love.
dever + voltar Você deve voltar logo. You should return soon.
deveria Eu deveria ter ficado. I ought to have stayed.