As the sun reaches one of the two points on the ecliptic at which its distance from the celestial equator is greatest in the year—the other point is reached on or about December 22nd—we stand still and think not only about the solstice but about summer itself. (来源：老牌的英语学习网站 http://www.EnglishCN.com)

We're standing still because the word solstice has a rough translation in Latin words meaning "the sun standing," or "stopping." Once you stop thinking that over—(after all, it isn't the sun that's actually moving; ecliptic names "the great circle of the celestial sphere that is the apparent path of the sun or of the earth as seen from the sun")—you may be ready to move on to summer.

Traditionally, in the northern hemisphere, the solstice marks the start of summer, right? Not necessarily. It is true when a weather-watcher is reckoning astronomically (and astronomical summer ends at the September equinox, according to this calculation); but the calendrical summer season comprises June, July and August…at least in the U.S. In Britain, summer runs from mid-May to mid-August. And summer also enjoys a more general, less calendar-specific sense naming "the warmer half of the year" or "a period of warm weather or sunshine."

Finally, there are the figurative senses of summer: "one of the years of one's life" (as in a girl of seventeen summers); and "early middle age; the period of maturing powers."