In English, adverbs are frequently formed by adding "-ly" to the end of an adjective; in Spanish, they are frequently formed by adding -mente to the feminine form of adjectives. However, there are many adverbs in both languages that do not fit this pattern. In Spanish it is more common than in English for adjectives to function as adverbs.
In both languages, it is common for phrases to function as adverbs. For example, in the sentence "he fought with courage" (luchó con coraje), "with courage" (con coraje) is an adverbial phrase.
A sentence that modifies an entire sentence is known as a sentence adverb and usually indicates the speaker's attitude toward what the sentence says. For example, in the sentence "thankfully, it was nothing serious" (afortunadamente no fue nada serio), "thankfully" (afortunadamente) is a sentence adverb.
