get可作系动词，也可用于进行时态，表示“渐渐......；愈加......”。在is getting中，is不是“系动词”，而是“助动词”，它与系动词的目前分词getting构成进行时态。又如：
Bob is growing old.鲍勃日渐变老了。
The sky is turning bright in the east.东方已露出鱼肚白。
Mother was becoming too frail to live alone.妈妈已渐渐衰弱到没办法独居。
It is getting warmer and warmer over the next few days.在将来几天里，天气会愈加暖和。
▲正如曹老师说的，be动词有时也可用于进行时。
“be + being + adj.” 有两种意义：① 强调某人在某个时候暂时性的神态或举止；② 某人故意表现出来的神态或举止。假如指某人一贯性的情况，就应该去掉being。试比较：
You are clever. 你非常聪明。（一贯性）
You are being clever. 你目前倒非常聪明。
You are being clever. 你在耍小聪明。
He is stupid.
He is being stupid.
He is being stupid.
