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sexual act; sexual intercourse
性行為には避妊の知識が不可欠だ。
Knowledge of contraception is essential for sexual activity.
同意のない性行為は犯罪として厳しく罰せられる。
Non-consensual sexual acts are severely punished as a crime.
性感染症は性行為を通じて広がるため定期検査が重要だ。
Regular testing is important because sexually transmitted infections spread through sexual contact.