# X factor

idiom

Source: https://englishreference.com/idiom/x-factor
Updated: 2026-08-10

## Meaning

An unknown or hard-to-define influence; a factor with unknown or unforeseeable consequences.

## Examples

- Her unique voice is the X factor that makes her a star.
- The team played well, but their new captain provided the X factor that led them to victory.
- While the candidate possessed all the necessary technical qualifications, it was his undeniable charisma that served as the decisive X factor during the final interview.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.