This gives more information about the verb and about how the action was done. The same form of the adjective is used for both singular and plural nouns. Remember that adjectives in English have no plural form.
It links the subject, in this case "writing a dissertation," to the complement or the predicate of the sentence, in this case, "hard.") (The "be" verb is also sometimes referred to as a copula or a linking verb. It takes a good deal of dedication to complete a doctoral degree.This expresses what the person, animal, place, thing, or concept does. His research findings can contribute to social change.The author presented the results in Chapter 4.
Nouns are typically used as subjects, objects, objects of prepositions, and modifiers of other nouns. The name of something, like a person, animal, place, thing, or concept.