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Synonyms for rapidly include quickly, swiftly, speedily, fast, and at great speed. These words describe something happening at a high rate of speed or within a short time. Depending on context, alternatives such as promptly, hastily, briskly, and expeditiously can express more specific shades of meaning.
Quick Answer
The most common synonym for rapidly is quickly.
Other useful alternatives include:
- Swiftly: with great speed
- Speedily: quickly, especially in completing something
- Fast: at high speed
- Promptly: without delay
- Hastily: very quickly, often with little care
- Briskly: quickly and energetically
- Expeditiously: quickly and efficiently, often in formal writing
- At once: immediately, when rapidly refers to quick action rather than speed
The best choice depends on whether you want to emphasize speed, urgency, efficiency, or lack of care.
Quick Comparison Table
| Word | Meaning | Example |
| Rapidly | At a very fast rate | The company is growing rapidly. |
| Quickly | In a short time or at high speed | She quickly finished the report. |
| Swiftly | With great speed | The police acted swiftly. |
| Promptly | Without delay | Please respond promptly. |
| Hastily | Very quickly, often without enough thought | He made a hasty decision. |
| Expeditiously | Quickly and efficiently | The request was handled expeditiously. |
Definition
Rapidly: In a very short time or at a very fast rate.
Quickly: In a short time or at high speed; it is the closest everyday synonym for rapidly.
Learning Outcomes
After reading this guide, you will know:
- The closest synonyms for rapidly
- How quickly, swiftly, and promptly differ
- Which alternatives work best in formal writing
- Why hastily is not always interchangeable with rapidly
Useful Synonyms for Rapidly
1. Quickly
Meaning: At high speed or within a short time.
The temperature is rising quickly.
Best for: Everyday English, conversation, and general writing.
Quickly is usually the safest replacement for rapidly.
2. Swiftly
Meaning: With great speed, often suggesting efficient or decisive action.
The manager swiftly resolved the problem.
Best for: Actions, decisions, responses, and movement.
Rapidly can describe a process or rate, while swiftly often highlights how quickly an action is performed.
3. Speedily
Meaning: Quickly or in a short amount of time.
The application was processed speedily.
Best for: Completion of tasks or processes.
It is accurate but somewhat less common than quickly or swiftly.
4. Fast
Meaning: At high speed.
Technology is changing fast.
Best for: Informal and everyday English.
Fast is especially natural after verbs such as grow, change, move, and run.
5. Promptly
Meaning: Without delay.
The customer service team responded promptly.
Best for: Responses, actions, replies, and professional communication.
Important: Promptly emphasizes lack of delay, not necessarily physical speed.
6. Briskly
Meaning: Quickly and energetically.
She walked briskly toward the station.
Best for: Walking, movement, activity, or energetic behavior.
It adds an idea of energy, which rapidly does not necessarily express.
7. Hastily
Meaning: Very quickly, often without enough thought or care.
He hastily signed the agreement.
Best for: Decisions or actions performed too quickly.
Hastily is not a neutral synonym. It can suggest that the speed caused a mistake or poor judgment.
8. Expeditiously
Meaning: Quickly and efficiently.
The complaint was handled expeditiously.
Best for: Formal, professional, legal, or administrative writing.
It emphasizes efficient completion, rather than simply high speed.
9. At Once
Meaning: Immediately or without delay.
She called the doctor at once.
Best for: Situations requiring immediate action.
This is closer to immediately than to rapidly, so it cannot replace rapidly in every sentence.
10. In Short Order
Meaning: Very soon or quickly.
The problem was resolved in short order.
Best for: Informal and conversational writing.
It usually refers to something being completed quickly rather than something moving at a high speed.
Context Matters: Which Synonym Should You Choose?
The meaning of rapidly can shift slightly depending on what it describes.
When describing a rate of change
Use:
- Quickly
- Swiftly
- Fast
- At a rapid pace
- The population is growing quickly.
- The population is growing fast.
Here, quickly and fast are natural replacements.
When describing an action
Use:
- Swiftly
- Quickly
- Promptly
The government responded rapidly to the crisis.
Possible alternatives:
The government responded swiftly to the crisis.
The government responded promptly to the crisis.
Swiftly emphasizes speed, while promptly emphasizes responding without delay.
When speed suggests poor judgment
Use:
- Hastily
- Impulsively — when the action is driven by sudden emotion rather than simply speed
She rapidly made a decision.
If the intended meaning is that she made the decision too quickly and without enough thought, hastily is more precise:
She hastily made a decision.
In formal writing
Use:
- Swiftly
- Expeditiously
- Promptly
The matter was dealt with rapidly.
More formal alternatives might be:
The matter was dealt with expeditiously.
or
The matter was addressed promptly.
Expeditiously is particularly useful when both speed and efficiency matter.
Meaning & Usage: Important Differences
Rapidly vs. Quickly
These are the closest pair.
- Rapidly often describes a high rate of change or movement.
- Quickly is broader and more common in everyday English.
The disease spread rapidly.
She quickly answered the question.
Both words can overlap, but quickly works in a wider range of ordinary situations.
Rapidly vs. Swiftly
Swiftly often describes an action performed with speed and decisiveness.
The company is rapidly expanding.
The company acted swiftly after the complaint.
The first focuses on rate of growth; the second focuses on speed of action.
Rapidly vs. Promptly
Promptly means without delay.
Please reply promptly.
This does not necessarily mean the reply itself is produced at high physical speed. It means the person does not wait before responding.
Rapidly vs. Hastily
These should not always be treated as interchangeable.
Rapidly is usually neutral:
The river is rising rapidly.
Hastily can imply poor judgment:
He hastily accepted the offer.
Calling something hasty often suggests too much speed and too little thought.
Rapidly vs. Expeditiously
Expeditiously is more formal and often suggests that something is completed efficiently as well as quickly.
The application was processed expeditiously.
It is particularly suitable for professional and administrative contexts.
Example Sentences
Here are natural ways to replace rapidly in different contexts:
- The child quickly learned how to ride a bicycle.
- The firefighters swiftly responded to the emergency.
- Please deal with the request promptly.
- The new technology is spreading fast.
- She walked briskly through the park.
- The paperwork was completed speedily.
- He made the decision hastily and later regretted it.
- The case was handled expeditiously by the department.
- The situation changed rapidly after the announcement.
Grammar & Word Class
Rapidly is an adverb.
It modifies verbs and tells us that something happens at a fast rate.
- The economy is changing rapidly.
- The child grew rapidly.
- The situation developed rapidly.
Most of the alternatives above are also adverbs:
| Adverb | Related adjective |
| rapidly | rapid |
| quickly | quick |
| swiftly | swift |
| speedily | speedy |
| promptly | prompt |
| briskly | brisk |
| hastily | hasty |
| expeditiously | expeditious |
A useful grammar point
Do not confuse rapid and rapidly.
The company experienced rapid growth. ✅
The company grew rapidly. ✅
Rapid is an adjective, while rapidly is an adverb.
Common Mistakes
Mistake 1: Treating every synonym as identical
❌ He hastily completed the task when you only mean that he completed it quickly.
✅ He quickly completed the task.
Hastily can imply that he acted without enough care.
Mistake 2: Using “promptly” for every kind of speed
❌ The car was moving promptly.
✅ The car was moving rapidly.
Promptly normally refers to doing something without delay, not moving at a high speed.
Mistake 3: Overusing formal vocabulary
Expeditiously is grammatically correct, but it may sound unnecessarily formal in casual conversation.
We need to fix this quickly. ✅
is more natural in everyday speech than:
We need to fix this expeditiously.
Expert Tip
Choose the synonym according to the kind of speed you mean:
rapidly = fast rate
quickly = general fast action
swiftly = fast and decisive
promptly = without delay
hastily = too quickly or without enough thought
expeditiously = quickly and efficiently
This distinction makes your writing more precise rather than simply replacing one word with another.
Mini Practice
Choose the best alternative:
1. The company is ______ expanding into international markets.
A. promptly
B. rapidly
C. hastily
Answer: B. rapidly
The sentence describes a high rate of growth, so rapidly is the most natural choice.
2. Please respond ______ to this email.
A. promptly
B. briskly
C. rapidly
Answer: A. promptly
Promptly means without delay, which fits a request for a response.
Short Questions & Answers
Q: What is the closest synonym for rapidly?
Quickly is the closest common synonym for rapidly. Both can describe something happening at a high speed or within a short time.
Q: Is “swiftly” a synonym for rapidly?
Yes. Swiftly means with great speed and is especially natural when describing quick, decisive actions.
Q: Is “hastily” always a synonym for rapidly?
No. Hastily adds the idea that something was done too quickly, often without enough care or thought.
Q: What is a formal synonym for rapidly?
Expeditiously can work in formal contexts when the meaning involves completing something quickly and efficiently. Swiftly and promptly are also useful formal alternatives depending on context.
Key Takeaways
Quickly is the best general synonym for rapidly, but the alternatives are not completely interchangeable.
- Quickly: general, everyday speed
- Swiftly: speed with decisiveness
- Speedily: quick completion
- Fast: high speed, often informal
- Promptly: without delay
- Briskly: quickly and energetically
- Hastily: too quickly or without enough thought
- Expeditiously: quickly and efficiently
For precise writing, choose the word that expresses the specific kind of speed you mean.
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Amna Akhtar is a writer dedicated to making English easier to understand. She creates research-informed guides on grammar, vocabulary, spelling differences, antonyms, and synonyms, combining careful research with clear, practical explanations. She is also the co-author of the peer-reviewed research article “Determinants of Jobs Satisfaction of Female Teachers: An Evidence from District Hafizabad, Pakistan,”
