What word can be an adjective and adverb?

There are many words that can be both adjectives and adverbs. Here are a few examples:

* Fast: "He's a fast runner." (adjective) "He ran fast." (adverb)

* Slow: "The slow train was delayed." (adjective) "The train moved slowly." (adverb)

* Hard: "It's a hard decision." (adjective) "She worked hard." (adverb)

* Early: "We had an early start." (adjective) "We arrived early." (adverb)

* Late: "She was late for work." (adjective) "He arrived late." (adverb)

Note: Sometimes, the adverb form may end in "-ly" (e.g., "slowly," "hardly"). However, many adverbs don't.