noun
untruth
un-TROOTH/ˌʌnˈtruːθ/
The quality of being false, or a false statement.
The claim that the jar is empty is an untruth.

Etymology
Negating truth in its older sense of faithfulness produced a word for treachery or disloyalty. The meaning later shifted to falsehood and an individual false assertion, connecting untruth with statements rather than personal loyalty.
In context
your opinion is a lie it's not true you told an untruth and you said it's your opinion
More examples
- Children sometimes tell untruths to avoid getting into trouble.
- The untruth of the accusation is clear from the records.
- Repeating an untruth does not make it true.
Forms
untruth · untruths
untrue adjective — Not true or consistent with facts.
Similar words
- falsehood
- Similarly names either a false statement or the quality of falseness.
- lie
- Specifically means a false statement made with intent to deceive.
- inaccuracy
- Can describe a mistaken detail in an otherwise true account.