Whether to write runaway or run away depends on how the words function in the sentence. Use runaway (one word) as an adjective meaning someone who has left home without permission, an uncontrolled escalation, or something that has slipped from regulation. Use run away (two words) as a verb phrase meaning to depart quickly or to escape a situation. This guide explains the grammar rules, offers clear examples, and includes a quick reference table so you can choose the correct form every time.
Quick Reference: Runaway vs Run Away
Use this table when you need a fast, reliable check.
| Form and Part of Speech | When to Use | Position in Sentence | Example |
|---|---|---|---|
| Runaway (adjective) | Describes a noun: someone who has escaped, or something escalating or uncontrolled | Before a noun or after a linking verb | runaway child, runaway train, runaway inflation |
| Run away (verb phrase) | Express the action of leaving quickly or escaping | Verb position, often with a subject | She might run away tonight |
| Runaway (noun) | Refers to a person who has fled, commonly a child | Subject or object of a verb | The runaway was found at a friend’s house |
| Run away (phrasal verb) | Used with objects to mean escaping from something | Verb + particle + optional object | He can’t run away his problems |
Runaway as an Adjective
As an adjective, runaway describes something that has escaped control or increased rapidly. It commonly modifies nouns such as train, child, success, or emotion. You will see it before a noun or after a linking verb such as is or became. No preposition is needed. Writers often use runaway in business, economics, and technology to signal fast, sometimes concerning, growth. In personal contexts, it refers to minors who leave home without permission. In broader usage, it describes processes or situations that accelerate beyond regulation or expectation.
Examples of Runaway as Adjective
- The runaway train was finally stopped by emergency crews.
- After a runaway success in its first week, the app reached the top of the charts.
- Social services took the runaway teen to a shelter.
- Inflation became runaway when prices rose more than 10 percent month over month.
Run Away as a Verb Phrase
As a verb phrase, run away describes the action of leaving quickly, often to avoid detection, responsibility, or danger. It functions like any other verb and can appear with helping verbs, modals, and negations. You can use it transitively with an object to indicate escaping from something, or intransitively to indicate departing. Common complements include from, from under, and figurative situations such as stress or debt.
Examples of Run Away as Verb Phrase
- The prisoner tried to run away during the night.
- She felt the urge to run away from her stressful job.
- They cannot run away their obligations forever.
- If the storm worsens, we may need to run away to higher ground.
Runaway as a Noun
Runaway also functions as a noun, referring to a person who has fled, typically a child who has left home. It can also name a vehicle that cannot be controlled, such as a train or car. In social service and legal contexts, runaway is a standard term for a minor who is missing because they left their caregiver. Using the noun form is clear and widely understood in professional and public communication.
Examples of Runaway as Noun
- A runaway was located at a relative’s house after three days.
- The railway labeled the train a runaway after it passed red signals.
Common Mistakes and How to Avoid Them
Speakers and writers sometimes confuse the forms by choosing the wrong part of speech or placing the two-word verb incorrectly. To avoid errors, first decide whether you need a descriptor, a noun, or an action. If you are describing a noun, use runaway as a single word adjective. If you are describing an action, use the two-word verb run away. Do not insert runaway between a verb and its object; in those cases, the two-word verb run away is required. Proofread by asking whether the word is describing, naming, or acting; this helps you choose the correct form consistently.
Regional and Stylistic NotesRegional and Stylistic Notes
Both runaway and run away are standard in American and British English, but they follow the same grammar rules in all varieties. In formal writing, prefer runaway as an adjective or noun and run away as a verb phrase. Headlines and labels sometimes use runaway alone for brevity, such as in terms like runaway train or runaway inflation, because the single word efficiently conveys loss of control. In narrative contexts, the verb form run away more naturally conveys the act of leaving. Choosing the correct form depends on grammar, not region.
Summary
Use runaway as an adjective or noun to describe an uncontrolled situation or a person, often a child, who has escaped. Use run away as a verb phrase to describe the action of escaping or leaving quickly. Pronunciation and spelling are the only differences between the forms; the distinction is grammatical. By matching the word form to its role in the sentence, you can communicate precisely and avoid common errors in both writing and speech.