Lack is a synonym of Need. Need is related to Box. Box is related to Sock. Sock is related to Single. 
Double is related to Twin. Twin is a synonym of Counterpart. 
Lack <--Synonym--> Need <--RelatedTo--> Box <--RelatedTo--> Sock <--RelatedTo--> Single 
Double <--RelatedTo--> Twin <--Synonym--> Counterpart 