lack vt.& n.缺乏;缺少; 不足
(教材P49)When there is a lack of food, there is hunger.
当缺少食物时就会有饥饿产生。 
 
(1)(a) lack of...                              ……的缺少
for lack of sth.                              因缺少……
(2)lacking adj.                               缺少的;缺乏的
be lacking in                                 缺少……;……不足  
Health problems are closely connected with bad eating habits and a lack of exercise.
健康问题与不良饮食习惯和缺乏运动有密切关系。