候 hòu is built on 亻 (rén, person) plus a watching element. The left side is the standing-person radical 亻, the form 人 takes when it leans against another component. The right side carries an old sense of peering out and keeping watch, the same family as 侯 hóu, the lord who held a frontier post. Put together, 候 pictures a person posted to look out and stand by: a watcher, a sentry, someone waiting for a sign on the horizon.

From that figure of one who waits and watches, three senses fan out:

1. The bound word for time and the weather. 候 rarely stands alone today; its commonest life is inside two-syllable words. It supplies the "when" of 时候 shíhou (time, moment) and the long-term weather of 气候 qìhòu (climate).
2. To wait, to await. The direct verb sense: 等候 děnghòu (to await), 候车 hòu chē (to wait for a bus or train), 候诊 hòuzhěn (to wait to see a doctor). Here 候 is a more formal cousin of 等 děng.
3. Season, period, the unit of climate time. In the old calendar a 候 was a five-day span, three of them to a 节气 jiéqì (solar term). This is the 候 that ties weather to the turning year.

The thread through every sense is waiting measured against time. The sentry waits for what the day brings; 时候 is the moment you wait to arrive; 气候 is the slow weather you wait out across a season. 候 is the person on watch, and the time being watched.

For most learners the first and most important 候 lives inside one word: 时候 shíhou. It is the everyday "time" in the sense of "when," the moment or stretch at which something happens. 什么时候 shénme shíhou is "when?", the single most useful time-question in the language. 小时候 xiǎo shíhou is "when (I was) little," childhood. The pattern ...的时候 ...de shíhou turns any clause into "when ...": 吃饭的时候 "while eating," 我来的时候 "when I came." Note the second syllable goes neutral (shíhou, not shíhòu) in this everyday word.

Keep 时候 apart from 时间 shíjiān. 时候 answers "at what point" (a moment on the timeline). 时间 answers "how much" (a duration, a quantity of time you can have, spend, or run out of). 现在几点钟 asks the clock; 你有时间吗 asks whether you have duration to spare. The two are not interchangeable.

The other major life of 候 is the slow time of the weather. 气候 qìhòu joins 气 qì (air, vapor, the breath of the atmosphere) to 候 (the season) and names the climate: the long-run pattern of a place, not the day-to-day. This is the 候 of the old farmer's calendar, where a 候 was a five-day unit and weather, crops, and ritual all turned on the season's rhythm. From the same root come 候鸟 hòuniǎo (migratory bird, the creature that times its flight to the season) and 火候 huǒhou (literally "fire's season," the cook's exact heat-and-timing).

Distinguish 气候 from 天气 tiānqì. 天气 is today's weather, the sun or rain you step out into this morning. 气候 is the standing climate of a region, what you would tell someone packing for a year abroad. 北京的气候 is "Beijing's climate"; 今天的天气 is "today's weather."

Picture a sentry, 亻 the person, posted at the edge of a road, peering out and waiting for a sign. That figure of one who watches and waits is the whole of 候. Hold the image and the senses follow.

What the sentry waits for is a moment: that is 时候, the "when" of 什么时候 and 小时候. The act of standing by is 等候, the formal waiting of a station sign. And the slow weather the watcher endures across a turning season is 气候, the climate. One person on watch, three kinds of time. When you meet 候, ask which time is being awaited, and the meaning falls into place.