Modal verbs are auxiliaries used to express attitudes or feelings generally
in relation to an infinitive. They correspond in English to phrases such as
‘you cango’, ‘you mustgo’, ‘you wantto go’, and ‘you haveto go’.
The most common Spanish verbs are several stating differing shades of obli-
gation: deber, tener que, haber. Others are poder, querer, saberand soler.Deber
Deber and deber deDeberon its own expresses obligation: ‘must’, ‘has/have to’, ‘should’,
‘ought to’:
Debe traerlo mañana. She must bring it tomorrow.
Ustedes deben exigir un You should demand a refund.
reembolso.
Deber deexpresses supposition or inference:
Deben de haber viajado ayer. They must have travelled
yesterday.
In practice, in contemporary usage native speakers do not always make this
clear distinction, sometimes using deberon its own to convey supposition:
El río no debe ser muy profundo‘The river can’t be very deep’.
However,deber deshould not be used to express obligation.Tenses of deberTenses other than the present of debersometimes pose problems for
English-speaking students.16.1.216.1.116.1