to make something deeper, or to become deeper

One way of preventing further flooding would be to deepen the river bed. 防止洪水再次泛滥的一个办法是深挖河床。

The sea bed deepens here to 5,000 metres. 此处海床变深至5000米。

to become more strongly felt or experienced, or to make something this way

Over the years, her love for him deepened. 这些年来，她对他的爱更深了。

The economic crisis is deepening. 经济危机正在加重。

We must try not to deepen existing splits within the party. 我们必须努力避免党内现有的各种分歧进一步扩大。

to make something increase or become more serious

It certainly helped to deepen my understanding of the situation. 它当然有助于加深我对整个情况的理解。

to become lower

Boys' voices deepen in their early to mid-teens. 男孩子十岁出头到十五六岁之间嗓音会变得低沉起来。

to become darker

The shadows deepened as the sun dropped below the horizon. 太阳落下地平线，夜色越来越浓。