Identify the part of speech of the underlined word in the following sentence: "The webinar should have ended earlier than it did".
earlier
Earlier is an adverb in this sentence.
Complete the following task based on the instruction and optional input provided.### Instruction:
Identify the part of speech of the underlined word in the following sentence: "The webinar should have ended earlier than it did".

### Input:
earlier

### Output:
Earlier is an adverb in this sentence.