A factor is one of the things that causes or influences a result; an element that contributes to an outcome. When multiple things affect a situation, each of them is a factor.
What Does Factor Mean?
Factor comes from Latin factor, meaning "maker" or "doer", from facere (to make or do). In modern English it is used to describe any element, condition, or circumstance that plays a role in bringing about a particular result or situation. The word is neutral — a factor can be positive, negative, or simply informational.
Factor is especially common in academic writing, business, science, and journalism. You will often see it with adjectives that signal importance: key factor, major factor, significant factor, contributing factor. The plural factors is very frequent when analysts or writers are listing the causes of something.
Factor can also be used as a verb in the phrasal verb factor in (or factor into), meaning to include something as part of a calculation or plan: "We need to factor in the cost of accommodation." This verb use is common in planning, finance, and project management contexts.
A common ESL confusion is using factor where reason would be more natural, or vice versa. A reason directly explains why something happened; a factor is one of several contributing causes. Both can often be used, but factor implies a more complex, multi-cause situation.
Example Sentences
| Sentence | Usage note |
|---|---|
| Price is the most important factor for many consumers. | key factor — consumer context |
| Several factors contributed to the company's success last year. | plural factors — business writing |
| Age is a significant risk factor for this condition. | risk factor — medical/scientific |
| You need to factor in the travel time when planning your day. | factor in — verb (phrasal) |
| The weather was a deciding factor in our decision to cancel the event. | deciding factor — everyday use |
| Motivation is a key factor in language learning success. | academic / educational register |
| We must factor the delivery costs into the overall budget. | factor into — formal/business |
| Stress is often cited as a contributing factor in workplace accidents. | contributing factor — formal report |
Word Forms
| Form | Word | Example |
|---|---|---|
| Noun (singular) | factor | Cost is a factor. |
| Noun (plural) | factors | Many factors affect the result. |
| Verb (base) | factor | Factor in the extra costs. |
| Verb (past) | factored | We factored in all the risks. |
| Verb (gerund) | factoring | Factoring in travel time is essential. |
| Adjective | factorial | Factorial notation is used in maths. |
Common Collocations
| Collocation | Example phrase |
|---|---|
| key factor | Price is a key factor in the decision. |
| major factor | Lack of sleep is a major factor in poor performance. |
| contributing factor | Stress was a contributing factor in his illness. |
| deciding factor | The location was the deciding factor for us. |
| risk factor | Smoking is a well-known risk factor for cancer. |
| significant factor | Experience is a significant factor in hiring. |
| factor in | Did you factor in the cost of repairs? |
| external factor | Exchange rates are an external factor we cannot control. |
Synonyms
Antonyms
Common Mistakes
Watch Out For
The main factor of her success was hard work.
The main factor in her success was hard work. (Use "in", not "of", after factor when describing a situation.)
There are many factors of this problem.
There are many factors contributing to this problem. (Factor does not typically take "of" in this pattern — use a verb phrase instead.)
We need to factor the extra time.
We need to factor in the extra time. (The phrasal verb is "factor in" or "factor into" — it always needs a particle.)