Being of the same sex/gender. The term is used in contexts such as sexual orientation or marriage (e.g., same-sex).
同性婚についての議論が社会で活発になっている。
Debates about same-sex marriage are becoming active in society.
同性の友達と旅行に行くのは気楽で楽しい。
Traveling with friends of the same sex is easygoing and fun.
この調査では同性・異性の交友関係についても質問している。
This survey also asks about friendships with same-sex and opposite-sex people.