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Sweden's Supreme Court on Friday threw out an appeals court ruling acquitting a man of raping a 10-year-old girl because it had been unsure what the word she used for her vagina meant.

The girl had used the word "snippa", devised by the Swedish Association for Sexuality Education (RFSU) in the early 2000s and introduced in preschools as a neutral and informal term to destigmatise women's genitals.

It is intended to be the female equivalent of the existing and commonly-used word "snopp" for male genitalia, and has rapidly grown in usage since its introduction.

In June 2021, the Halmstad district court in southwestern Sweden convicted the man, who is in his 50s but has not been publicly named, of rape for putting his hand inside the girl's pants and touching her vagina.

But a panel of appeals court judges overturned the ruling in February 2023, saying they could not conclude with certainty what the girl was referring to because she used the word "snippa".

The dictionary defines "snippa" as the outer part of female genitalia but in common usage it refers to the entire vagina, not just the vulva.

Despite the girl testifying that the man's fingers had been "inside" her "snippa", the appeals court also said it could not conclude that the man had penetrated her vagina because of the use of the word "snippa".

Penetration is required for a rape conviction.

The appeals court ruling caused an uproar among legal experts, health authorities and the public, prompting several demonstrations across Sweden, with the hashtag #jagvetvadensnippaar ("I know what a snippa is") going viral on social media.

The Supreme Court ordered a new panel of appeals court judges to retry the case.

"The court is not bound by the criminal classifications presented by the prosecutor but by the prosecutor's description of the act," the Supreme Court said.

"In the snippa case, the Court of Appeal found it was proven that the man had touched the girl's sexual organs, and the court should therefore have looked at alternative classifications," it said.

"It must have been clear to the Court of Appeal that there was another penalty provision that could have been applicable - sexual abuse of a child," wrote Stefan Johansson, one of the judges who participated in the Supreme Court's decision.

The girl's mother welcomed the ruling, writing in a text message to Swedish Television: "A big weight has been lifted."

The ruling was "important for children's right to the rule of law, and ... for my daughter's emotional well-being and faith in the rule of law".