lucid
/ˈlu:sɪd; `lusɪd/ adj
1 clearly expressed; easy to understand 表达清楚的; 易懂的
a lucid explanation 明白的解释
His style is very lucid. 他的文体很明畅.
2 clear in one's mind; sane 头脑清晰的; 清醒的
lucid intervals, ie periods of sanity during mental illness 清醒期（精神病发作的间歇期）.