The Subjunctive with Doubt, Disbelief and Denial

The main clause implies uncertainty or negativity AND the subject changes...

Requires subjunctive forms of verbs in the end, or subordinate, part of the sentence.

Dudar

To Doubt

Negar (e:ie)

To Deny

No Creer

Not to believe

No Estar Seguro/a (de)

Not to be sure

No es cierto

It's not true; It's not certain

No es seguro

It's not certain

No es verdad

It's not true

Es imposible

It's impossible

Es improbable

It's improbable

(no) es posible

It's (not) possible

(no) es probable

It's (not) probable

Sentences with NO DOUBT or UNCERTAINTY... (expressions of certainty)

Require the indicative form of verbs at the end, or subordinative, part of the sentence.

No dudar

Not to doubt

No cabe duda de

There is not doubt

No hay duda de

There is no doubt

No negar (e;ie)

Not to deny

Creer

To believe

Estar seguro/a (de)

To be sure

Es cierto

It's true; It's Certain

Es seguro

It's certain

Es verdad

It's true

Es obvio

It's obvious