Chinese phrase
参加是自愿的 cān jiā shì zì yuàn de
Meaning
Participation is voluntary
When to use it
It says that taking part is a free choice, not a duty. It often reassures people that they may choose whether to join.
Example dialogue
我们要报名夏季实习，你会参加吗？ wǒ men yào bào míng xià jì shí xí nǐ huì cān jiā ma
We're signing up for a summer internship - will you take part?
我还没决定。组织者说参加是自愿的，可以先旁听。 wǒ hái méi jué dìng zǔ zhī zhě shuō cān jiā shì zì yuàn de ké yǐ xiān páng tīng
I haven't decided yet. The organizer said participation is voluntary, and we can sit in and observe first.