名词 interval:

1. a definite length of time marked off by two instants

2. a set containing all points (or all real numbers) between two given endpoints

3. the distance between things

4. the difference in pitch between two notes

George struggled wildly, going under and resurfacing at regular intervals.

乔治疯狂地挣扎，不断在水面上浮浮沉沉。

Make a point of backing up your files at regular intervals.

一定要定期备份文件。

The cartridge must be replaced at regular intervals.

弹药必须定时更换。

Cars passed at irregular intervals.

断断续续地有汽车驶过。

At intervals there were red warning lights.

红色警示灯一明一灭地闪着。

Kites whooshed above the beach at intervals.

风筝在沙滩上空时隐时现。

The forecast said there would be sunny intervals and showers.

预报间晴，有阵雨。

Meetings take place at fortnightly intervals.

每两周开一次会。

These cars are put at intervals of three meters.

这些车每隔三米放一辆.

Flaming torches were positioned at intervals along the terrace.

沿台阶每隔一段距离布置有燃烧着的火炬.

The doctor visits his patients at their homes at regular intervals.

那医生定期到病人家出诊.

The bell rang at 20 - minute intervals.

每隔20分钟,钟敲响一次.

He visits us at irregular intervals.

他不定期地来探访我们.

Trains are running at 15 - minute intervals.

火车每间隔15分钟开一班.

It'snowed at intervals this week.

这星期不时下雪.