The next sin that Mishnah Daled (Mishnah 4) mentioned was committing adultery by having relations with a na'arah hame'orasa. There are three stages in the development of a young woman. She's a ketanah until she's 12 years old and hits puberty. Once she hits that point, she is a na'arah. She is on the next stage for a period of six months. After those six months pass, she is a bogeret, which is a full-fledged adult. So she has to be a na'arah over here, and she also has to be a me'orasa. She has to be somebody engaged, but not married halachically. That means the stage of erusin (engagement) happened, but the nisu'in (marriage) never happened.
In a regular case of adultery, the death sentence is strangulation. Here, specifically with the na'arah hame'orasa, the punishment would be stoning. We'll elaborate on when this applies. Somebody who has relations with a na'arah hame'orasa, an engaged na'arah, would only be liable to be stoned if she was of the age of a na'arah, that six-month period. She also never had relations with a man. She was engaged, but not fully married to that person. She's living in her father's house. If two men had relations with her, a na'arah hame'orasa, the first man who went with her would be obligated to be stoned because, when he went with her first, she was a betulah. She never had relations with the man. The second one is put to death by strangling because she wasn't within that category of a na'arah hame'orasa anymore. She had relations with the first man, so when she went with a second man, she wasn't considered to be a na'arah hame'orasa.