Sigma is the 18th letter in the Greek alphabet (Σ, σ) If you meant to ask what is a sigma male though: Sigma males are successful, good-looking, dominant, and influential people, but tend to be loners. It's sad that most men want that in the ሩቅ ምስራቅ. There, a man feels the needs to be sigma and a woman feels the need to be a feminist which is a sad reality because both lives encourage loneliness. Hope this helped. Good Day!