Fastly vs. Fast: Understanding Adverb Usage

The question asks us to replace the underlined word "fastly" in the sentence: "The car is moving very fastly on the road." We need to find the grammatically correct word to describe how the car is moving.

Identifying the Error in 'Fastly'

The word "fastly" is not a standard word in the English language. Often, students mistakenly add "-ly" to words like "fast" to form an adverb. However, the word "fast" itself serves as both an adjective and an adverb.

• As an adjective: "He drives a fast car." (Describes the noun 'car')
• As an adverb: "He drives fast." (Describes the verb 'drives')

In the given sentence, "very fastly", the word needs to modify the verb "moving", indicating the manner of movement. Therefore, an adverb is required.

Evaluating the Options

Let's examine the given options:

1. fastliness: This is not a recognized English word. It seems like an attempt to create a noun related to 'fast', but it's incorrect.
2. quickliness: Similar to 'fastliness', this is not a standard English word.
3. fast: This word can function as an adverb. "The car is moving very fast" is grammatically correct. 'Fast' correctly modifies the verb 'moving'.
4. quicker: This is the comparative form of the adjective/adverb 'quick'. It means 'more quick'. The sentence doesn't make a comparison, so the comparative form is not suitable here. We need the simple adverb form.

Why 'fast' is the Correct Replacement

The word "fast" correctly functions as an adverb in this context. It tells us *how* the car is moving. The adverb "quickly" could also be used, but "fast" is the correct adverbial form of the word "fast". The sentence requires a simple adverb, not a comparative one like "quicker", and "fastly" is not a valid word.

The Corrected Sentence

By replacing "fastly" with "fast", the sentence becomes grammatically correct:

The car is moving very fast on the road.