Alone; independently; by oneself — doing something without assistance or togetherness.
彼は単独で会社を立ち上げた。
He started the company by himself.
その山は経験者なら単独で登ることも可能だが危険も伴う。
Although experienced climbers can ascend that mountain alone, it also involves risks.
単独で決定するのではなく、チームで話し合おう。
Instead of deciding alone, let's discuss it with the team.