Consider what you are trying to accomplish with the word before you change the adjective. For example, the adjective "beautiful" is used to describe people, places, things and other nouns. To make the word "beautiful" describe a process, act or action, you must change it to an adverb.
Add "-ly" to words, such as beautiful, that do not end in a "-y". This simple letter addition creates an adverb from an adjective. It also changes your meaning from an appearance description to a commentary on behavior and action.
Change the "-y" at the end of adjectives to an "-ily" in order to create an adverb. The change is made to accommodate the awkward "-y" at the end of the adjective. For example, "ready" would become "readily."
Consider the new adverb before using it. You can change words like "hard" and "late" into adverbs "hardly" and "lately." However, by changing these words, you have also changed their meanings. "Hardly" does not describe a texture, but as an adverb, it is a frequency. "Lately" is no longer synonymous with "tardy" but with "recent." Other words, such as "fast," do not change to become adverbs.
Transform adjectives in Spanish to adverbs by adding "-mente" to the end of the word, as you would add "-ly" in English.