Affirmative adverbs
Affirmative adverbs are those that indicate the grade of certaintly about the action of the verb in the sentence. They modify the verb giving this type of information.
Some common affirmative adverbs are:
Sí, quiero ir al cine contigo.
(Yes, I want to go to the cinema with you.)
Realmente, me apasionan los coches de carrera.
(I really am passionate about racing-cars.)
Verdaderamente, su casa es más bonita que la mía.
(Trully, her house is prettier than mine.)
Seguramente me apunte a ese gimnasio.
(I most probably join that gym.)
Note that when they are formed by a group of words they are called "locuciones adverbiales", i.e. "lo más seguro" or "en verdad":
En verdad, no me gusta tanto ese chico.
(Trully, I don't like that guy so much.)
Lo más seguro es que suspenda el examen.
(Most probably I will fail the exam.)