词根：leth = death

  来自希腊语的leth意为death。同义词根有来自拉丁语的mort/mors/mor和来自希腊语的necr,thanat/than。

同源词：

1. lethargy （死后不动的状态leth(=death) + a(=not) + rg<erg(=work)）
  n.昏睡（状态）；无生气；嗜睡
  lethargic adj.昏睡（状态）的；嗜睡的；无生气的
  Normally i feel invigorated after exercise,but all i feel today is lethargy.平时做完运动我都感到精力充沛，但今天却觉得很没力气。

2. lethal
  adj.致命的
  lethal dose poison 足以致死的毒药量
  lethal weapons 致命武器
  lethal chamber （使用毒气的）无痛屠宰场

3. Lethe
  n.忘川（冥府一河流名，喝了河水可以忘记过去）；（亦作l～）忘却

词根：leth = oblivion （遗忘）

lethargy 昏睡（leth原意是“ 忘川”，喝了忘川水，一切都忘记）

lethal 致命的（忘了，死了）

词根词缀：lethal-, -lethal, -lethally; lethi-, letho-, leth-

【来源及含义】Latin: death, deadly; fatal, lifeless; kill, killing; die, dying; mortal, mortality; destructive

【相关词根词缀】 Related "death, dead; kill" units: -cide; mort-; neci-; necro-; phono-; thanato-.

【同源单词】hyperlethal, lethal, lethal chamber, lethal dose, lethal injection, lethal mutation

词根词缀：letho-, leth-

【来源及含义】Greek > Latin: lie hidden, secret; forgetfulness, forget, inactive through forgetfulness; also sleepy, drowsy, dull, sluggish

【相关词根词缀】 Related "sleep" units: dorm-; hypno-; narco-; oneiro- (dream); somni-; sopor-. Etymologically related "forget, forgetfulness" word families: aletho-; oblivio-. Related "memory, remember" word families: memor-; mne-.

【同源单词】alethia, lethargic, lethargical, lethargically, lethargize, lethargogenic