It is fairly clear that sleeping period must have some function,
很清楚，睡眠必然具有某種作用。
新概念英語(yǔ)第四冊(cè)
Lesson 19 The stuff of dreams
?? 句中詞匯解析
從本句中提取的重要詞匯
adv. 適當(dāng)，相當(dāng)?shù)?公平地;完全，簡(jiǎn)直;清楚地;
?? fair公平 + ly ...地→ ad.相當(dāng)；公平地
"The use of opium was not criminalized until fairly recently."
直到最近抽鴉片才被判定為非法。
近義：long, moderately, averagely, pretty, quite, rather
反義：undeservingly, unjustly, foully
n. 時(shí)期;（一段）時(shí)間;學(xué)時(shí);句號(hào);
adj. 具有某個(gè)時(shí)代特征的;（關(guān)于）過去某一特定歷史時(shí)期的;（家具、服飾、建筑等）某一時(shí)代的;
?? peri周圍，靠近+od道路→周期
"The overthrow of the military regime was followed by a period of anarchy."
軍事統(tǒng)治政權(quán)被推翻以后，接著是一段時(shí)期的無政府狀態(tài)。
近義：term, time, season, spell, bout, chapter
n. 功能，作用;應(yīng)變量，函數(shù);職務(wù);重大聚會(huì);
vi. 有或起作用;行使職責(zé);
?? funct活動(dòng)+ion表名詞 → 功能
"The function of the kidneys is to excrete wastes from the body."
腎的功能是排泄人體里的廢物.
近義：ceremony, operate, perform, run, work, interrelation
adj. 清楚的，明白的;清晰的，明亮的;清澈的;明確的;
adv. 完全地;清晰地;整整;
vi. 變明朗;變清澈;
vt. 掃除，除去;消除（嫌疑）;使清楚;使干凈;
n. 空隙，空間;
?? 可里耶（諧音）：可看見里面耶，表明是 清晰的
"The morning dawned fresh and clear after the storm at night."
夜里暴風(fēng)雨過后,拂曉清新而晴朗.
近義：illuminate, illustrate, rede, resolve, show, solve
反義：jumble, litter, mess, muss, scramble, shuffle
aux. 必須;必然要;（做出邏輯推斷）;（表示堅(jiān)持）;
n. 必須做的事，必不可少的事物;葡萄汁;霉臭;麝香;
vt.& vi. （表示必要或很重要）必須;（提出建議）應(yīng)該;得;（表示很可能或符合邏輯）一定;
adj. 不可或缺的;狂暴的;
"You must be able to speak French for this job."
干這項(xiàng)工作你得會(huì)說法語(yǔ)。
近義：ought, should, necessaries, necessity, precondition, prerequisite