useful是形容词词性。
useful 的常用短语：useful as可用作…的 can be used as
useful的用法例句：
1、In business a poker face can be very useful。生意场上，不动声色会非常有用。
2. "For heaven's sake!" Dot expostulated. "They're cheap and they're useful."拜托!”多特反驳道，“它们又便宜又管用。”
3. HDTV is especially useful if there are a lot of special effects.有很多特效的时候，高清电视就格外有用了。
4. The hinged seat lifts up to reveal a useful storage space.把用铰链连接的座位抬起来后，就会发现下面有一个实用的储物空间。
5. Pain-killers are very useful in small amounts to bring your temperature down.小剂量的止痛药对于降低体温非常有用。
6. From this chastening experience he learnt some useful lessons.从这次惨痛的经历中他得到了一些有益的教训。
7. Once our services cease to be useful to them, we're expendable.一旦我们的服务对他们不再有用，我们就可能被抛弃。
8. If you're converting your loft, these addresses will be useful.你要是打算改造阁楼，这些地址会派上用场。
9、Kurt hinted that she might be useful as a distributor of funds. 库尔特暗示,她也许可以当资金调配员。
10、This medicine is useful as a cure for colds. 这种药可用来治感冒。