Couple and pair
Couple: a husband and wife or a boyfriend and girlfriend.
Two couples remained on the dance floor.
Pair: two things of the same kind which go together.
Example: a pair of shoes, a pair of trousers
Despise and detest
Despise: have a very low opinion of someone or something; regard someone as worthless.
One must not despise the poor.
I detest the hot climate of Chennai.
Habit and custom
Habit: something which a person does so often that he does it without thinking about it
Custom: the usual or normal way of doing things
It is our custom to give presents on Christmas Day.
John has this nasty habit of making unpleasant remarks.
Leave and let
Leave: to go away from somewhere; to put something somewhere and allow it to stay there
Leave your shoes outside.
I left my coat in the bedroom.
Let: allow someone to do something; allow something to happen
Let him go.
Legible and readable
Legible: clearly written, easy to read
Readable: writing that is easy or pleasant to read
Your handwriting is not at all legible.
The book was full of technical jargon which made it hardly readable.
Patron and customer
Patron: person who supports financially the artistic or social work of a person or society
The artist thanked his patrons.
Customer: person buying things in a shop
He is a regular customer of ours.
People and person
Person: a man, woman or child
People: men and women in general; all those persons forming a nation or race
Government of the people by the people for the people
He is a nice person.