What Is the Past Tense of Cost? Meaning, Usage, and Examples
Understanding the past tense of common verbs is a cornerstone of learning English. Among these verbs, “cost” often causes confusion because it is irregular and does not follow the typical patterns most learners expect.
This article will examine what the past tense of “cost” is, how it is used in different contexts, and why it behaves differently from many other verbs. The discussion is supported by linguistic research, real-world examples, and practical usage cases, ensuring clarity for readers of all backgrounds.
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What is the past tense of cost?
The past tense of cost is cost. Unlike many English verbs that change form in the past (for example, play → played or teach → taught), the verb cost stays the same. In grammatical terms, it is categorized as an irregular verb with no change between the base form, past tense, and past participle.
Form breakdown:
| Verb form | Word |
|---|---|
| Base form | cost |
| Past tense | cost |
| Past participle | cost |
| Present participle | costing |
| Third-person singular | costs |
Why does cost not change in the past tense?
English has inherited many irregular verbs from Old English and Middle English. According to research in historical linguistics from Oxford University and the University of Cambridge, many high-frequency verbs remained irregular because they were preserved in daily use, while less common ones shifted into the regular -ed pattern.
The verb cost comes from the Old French couster and the Latin constare (meaning “to stand firm” or “to be valued at”). As English absorbed it, the form stabilized into the unchanged pattern we see today. Because cost is used in economic, legal, and daily contexts, it retained its irregular past tense through centuries of use.
How is cost used in sentences?
To master cost, it is necessary to see it in different sentence types. Below are four relevant examples for each tense or form.
Present tense
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The car costs too much for a student.
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This book costs more than the one on the shelf.
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It costs a lot to maintain a luxury home.
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The ticket costs fifty dollars.
Past tense
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The repair cost me five hundred dollars.
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Her mistake cost the company its reputation.
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The shoes cost less than I expected yesterday.
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His carelessness cost him the match.
Past participle
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The renovations have cost them a fortune.
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The war has cost many lives.
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The upgrades have cost more than the budget allowed.
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The policy has cost the government credibility.
Present participle
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He is costing the project incorrectly.
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They are costing the materials before approval.
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The accountant is costing the proposal line by line.
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She is still costing her mistakes from last year.
What is the difference between cost and other irregular verbs?
Learners often compare cost to other verbs that remain the same in past and present forms. Some of these include:
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cut → cut
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hit → hit
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let → let
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set → set
These verbs, like cost, are short, monosyllabic, and often connected to concrete actions or measurable values. Research from linguist Joan Bybee shows that shorter, high-frequency verbs resist regularization, which explains why cost remains unchanged in the past tense.
What are common mistakes learners make with cost?
1. Adding -ed
Some learners mistakenly write costed. While costed exists, it is only correct in certain technical uses (discussed below). For everyday meaning (“to have a price”), the correct past tense is always cost.
Incorrect: The car costed me ten thousand dollars.
Correct: The car cost me ten thousand dollars.
2. Mixing with price
Some confuse cost with price. While related, they serve different functions. Price is a noun that refers to the amount asked for, while cost is a verb that refers to the amount required to obtain something.
3. Misusing costed
In accounting or project management, costed is valid in technical English. It refers to the process of estimating or assigning costs. For example:
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The project was carefully costed before approval.
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The budget has been costed by the finance team.
But this should not be confused with the general verb meaning “to have a price.”
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When is costed acceptable?
As noted, in financial, managerial, and business English, costed appears in formal registers. The Cambridge Dictionary recognizes both cost and costed, but their usage differs:
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Cost (general past tense): The jacket cost fifty dollars.
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Costed (technical past tense): The engineers costed the project over two years.
Both forms are correct in their contexts, but in ordinary conversation, cost is the natural choice.
How can learners remember that cost does not change?
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Group learning strategy: Memorize it alongside other unchanged irregular verbs such as cut, hit, let, set.
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Repetition practice: Write sentences using cost in past and present forms.
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Contextual recall: When thinking of price or expense, associate it with “unchanged.”
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Mnemonic aid: “The cost never changes, not even in the past.”
Graphical Guide to Cost Verb Forms
| Tense/Form | Example Sentence |
|---|---|
| Present simple | The ticket costs ten dollars. |
| Past simple | The ticket cost ten dollars yesterday. |
| Past participle | The ticket has cost ten dollars every year. |
| Present participle | The clerk is costing the materials. |
| Technical use (costed) | The accountants costed the project. |
This table makes clear the difference between common and technical usage.
Why does understanding cost matter for learners?
Linguistic studies show that irregular verbs cause the greatest difficulty for second-language learners. Misusing them can affect clarity and credibility in communication. Since cost is common in business, economics, and everyday talk, mastery of its forms ensures accuracy in financial statements, professional writing, and ordinary conversation.
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Frequently Asked Questions (FAQ)
1. Is costed wrong?
Not always. Costed is acceptable in technical or accounting English, but not in everyday usage when talking about prices.
2. What is the difference between cost and price?
Cost is the amount paid to obtain something, while price is the amount asked for by the seller. For example, “The price of the book is $20, but it cost me only $15 with a discount.”
3. Does cost follow the -ed rule?
No. It is an irregular verb that remains the same in past and past participle.
4. Can I say “it has costed”?
No. The correct phrase is “it has cost.” Example: “It has cost me a lot of time.”
5. Why is cost irregular?
It remained unchanged because of its frequency and historical roots in Old French and Latin.
6. What is the past participle of cost?
It is cost. Example: “This mistake has cost them dearly.”
7. Is costed British or American English?
Costed is used in both British and American English, but only in technical financial language, not in everyday conversation.
8. What are some real-life examples of cost in past tense?
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The medicine cost too much last year.
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His decision cost him his career.
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The journey cost more than planned.
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Her success cost years of effort.
Conclusion
The past tense of cost is cost. It is one of those English irregular verbs that does not change across tenses, except when used in specialized accounting contexts where costed appears. Understanding its correct form is essential not only for clear grammar but also for accurate expression in business, economics, and everyday life. By grouping it with similar unchanged verbs, practicing with real examples, and recognizing its technical variation, learners can confidently use cost in any setting.