【Lack】 , 【want】 , 【need】 , 【require】 are comparable when meaning to be without something, especially something essential or greatly to be desired.
【Lack】 may imply either an absence or a shortage in the supply or amount of that something.
【Want】 frequently adds to 【lack】 the implication of urgent necessity and may be difficult to distinguish from its sense connoting longing (see under DESIRE ).
For this reason 【need】 may be preferred when a clear connotation of urgent necessity is desirable <he cannot get the rest he needs > 【Need】 usually throws the emphasis on urgent necessity rather than on absence or shortage, though both implications are often present.
【Require】 (see also DEMAND ) is often interchangeable with 【need】 but it may heighten the implication of urgent necessity.
