落后 (luò hòu): to lag behind; backward

If we don't work hard to learn new technology, we will soon lag behind our competitors.

The economic development of this region is relatively backward; the government is trying to attract investment.

In the race, he took the lead at first, but later he ran out of energy and gradually fell behind.

Due to inconvenient transportation, the education level in this mountain village has always lagged behind that of the city.