Slower vs more slowly: choosing the right form in English grammar

Slower or More Slowly? A Helpful Guide to Describing Speed in English

Let’s face it: English can be slippery when you’re talking about speed and how someone does something. Do you say “slower” or “more slowly”? The choice isn’t just about grammar; it shapes how clearly your idea lands. This little guide breaks down the rule so you can write with confidence, whether you’re reading a grammar note in a classroom, chatting in a study group, or bumping into a similar question in a test.

The short rule you can lean on

• Slower is an adjective. It describes a noun. Think: a slower car, a slower pace, a slower runner.

• More slowly is an adverb. It describes a verb—how an action is performed. Think: run more slowly, speak more slowly, move more slowly.

Here’s the thing: when you’re comparing how something is done, you’re usually talking about manner. That’s an action. For that, adverbs do the job, and with adverbs that have two or more syllables, we commonly use more. Slower doesn’t fit there as the adverb in standard, formal writing.

Let me explain with simple examples

Adjective for a noun (slower)

• The train was slower than last year. (slower describes the train—the noun)

• He has a slower pace than his teammates. (slower describes “pace,” a noun)

Adverb for a verb (more slowly)

• The train moved more slowly due to track work. (more slowly describes how the train moved, the verb)

• She explained the concept more slowly so everyone could follow. (more slowly describes how she explained, the verb)

A quick side note about a common gray area

Some people hear “slower” used with verbs and think it’s acceptable in everyday speech. It’s not wrong in casual talk, but in polished writing and standard grammar you’ll often see “more slowly” preferred for adverbial comparisons. The adjective “slower” sticks to nouns. If you want to describe the degree of an action, go with more slowly.

Why this distinction matters in real writing

• Clarity: If you say “The car is slower,” you’re saying the car’s quality is slower, which makes sense when you’re talking about the car itself.

• Precision: If you say “The car moves more slowly,” you’re focusing on the action—the speed of moving—how the car moves in that moment.

• Tone: Formal writing leans toward the clear adverb version for actions. In everyday speech, people sometimes mix them up, but you’ll sound more confident if you keep the rule in mind.

Set of handy rules of thumb

• If you can swap the word with a noun and still have a sensible sentence, you’re likely dealing with an adjective. Example: The slower bicycle won’t win the race. (Here, slower is about the bicycle as a thing.)

• If you’re describing how someone does something, you’re describing the manner of an action. Use more slowly: He spoke more slowly as he gathered his thoughts.

• If the comparison involves more than one syllable, many adverbs take more before the adjective form. For example, the phrase “more quickly” is typical for adverbs with two syllables or more.

A few everyday illustrations

• The coffee cooled more slowly on a rainy day. (describing how the cooling happened)

• The coffee is slower to cool when it’s in a metal mug. (describing the coffee as a noun, though you’d more naturally say “slower to cool” to keep it adjectival)

• The path along the park is slower for hikers in the fog. (the path’s pace is being described)

• The hikers moved more slowly through the mist. (manner of moving)

Where the mistake tends to sneak in

• If you say “The manager spoke slower about the plan,” you’re trying to describe the manner of speaking, but the sentence uses a comparative that feels off. The preferred form would be “The manager spoke more slowly about the plan.”

• If you write “The device runs slower,” you’re describing the device as a noun, and that can sound acceptable in casual speech, but in formal contexts you’d typically rephrase to the adverb form: “The device runs more slowly.”

A tiny, friendly quiz you can try in your own writing

• The room cooled more slowly this evening. True or false? (Answer: True, it’s the manner of cooling, an adverbial usage.)

• The room became slower as the air conditioner broke down. True or false? (Answer: False in natural English; you’d say “The room grew slower” is awkward here. You’d use “The room cooled more slowly” or “The room’s cooling slowed.”)

• Traffic moved more slowly during the construction. True or false? (Answer: True, it’s about how the movement happened.)

Putting it into real-world writing

When you’re drafting anything that involves speed or pace, pause and ask: am I talking about a thing (a noun) or about an action (a verb)? If it’s a noun, use slower. If it’s a verb, lean toward more slowly. The aim is to keep readers from stumbling over your grammar and to preserve the tempo of your writing.

A few everyday analogies to keep it relatable

• Think of adjectives as labels on people or things—they describe what something is. If you say, “That is a slower guitar,” you’re labeling the guitar.

• Think of adverbs as how you describe actions—like you’re narrating how something happens. If you say, “The guitarist plays more slowly,” you’re describing the act itself.

Why this topic matters beyond grammar worksheets

• Clarity in communication: In work emails, reports, or even casual posts, knowing whether you’re modifying a noun or a verb helps readers stay with your meaning.

• Consistency matters: If you start with “more slowly” in a paragraph, keep that pattern for similar comparisons. It creates a smoother read.

• Subtle tone control: Using the adverb form for actions often sounds more formal and precise, which can be helpful in professional writing.

A note on related forms

• Quick contrast you might hear in conversation: “More slowly” versus “slower.” The former is the standard adverbial form for comparisons; the latter is an adjective form used with nouns.

• Other pairs to watch: faster vs more quickly, louder vs more loudly, brighter vs more brightly. The same general rule applies: adjectives with nouns get the -er form (faster, louder); adverbs describing actions lean on more/most for the comparative (more quickly, more slowly).

A final thought to carry with you

Grammar is a tool for clarity, not a cage. The difference between slower and more slowly isn’t about making a sentence sound fancy; it’s about guiding your reader’s eye to the exact thing you want to describe. If you picture language as a conversation, slowing down the action with more slowly can help your listener feel the tempo as you intended. On the other hand, if you’re pointing to a property of the object itself, slower is the natural adjective choice.

So next time you’re choosing between slower and more slowly, ask:

• Am I talking about the noun or about the action?

• Is my goal to describe a thing’s pace or the way an action is carried out?

• Does the sentence read smoothly if I swap in more slowly?

If the answer points you toward the adverb, you’ve got a reliable path: more slowly.

Final takeaway

Slower and more slowly aren’t just two forms to memorize; they’re two doors to clearer writing. When you know which door to open, your sentences glide with intention—whether you’re analyzing how a race unfolds, describing a process, or simply explaining daily activities. And in the end, that’s exactly what good English writing is all about: making your meaning unmistakable, one well-chosen word at a time.