1. 平常的;不足为奇的
    If something is commonplace, it happens often or is often found, and is therefore not surprising.

    e.g. Foreign vacations have become commonplace...
           去国外度假已经变得很平常了。
    e.g. It is commonplace for snipers to open fire on aid convoys.
           狙击手向救援车队开火的事情很常见。

2. 平常的事;司空见惯的事
    A commonplace is something that happens often or is often found.

    e.g. It's become a commonplace to see people collapsing from hunger in the streets.
           现在在街上时不时会看见有人饿晕。

3. 老生常谈;陈词滥调
    A commonplace is a remark or opinion that is often expressed and is therefore not original or interesting.

    e.g. It is a commonplace to say that Northern Ireland is a backwater in the modern Europe.
           说北爱尔兰是现代欧洲死气沉沉的落后地区已是陈词滥调了。