1. 门槛;门口
    The threshold of a building or room is the floor in the doorway, or the doorway itself.

    e.g. He stopped at the threshold of the bedroom...
           他在卧室门口停住了。
    e.g. The bride was carried over the threshold.
           新娘被抱进了家门。

2. (某事发生或改变的)界限，阈，起始点
    A threshold is an amount, level, or limit on a scale. When the threshold is reached, something else happens or changes.

    e.g. She has a low threshold of boredom and needs the constant stimulation of physical activity...
           她容易厌倦，需要时常进行活动来刺激一下。
    e.g. The consensus has clearly shifted in favour of raising the nuclear threshold...
           显然大家已普遍开始转向支持提高核武器使用的门槛了。

3. 在…开端;将要经历;面临着
    If you are on the threshold of something exciting or new, you are about to experience it.

    e.g. We are on the threshold of a new era in astronomy.
           我们很快就将迎来天文学的新纪元。
    e.g. ...a lovely girl on the threshold of growing up.
           眼看就要长大成人的可爱女孩