one–to–one 
/ˌwʌntəˈwʌn/ adjective
/ˌwʌntəˈwʌn/ adjective 1 : involving two people who are dealing with each other directly
▪ We had a one-to-one meeting. 2 formal : perfectly matching one thing in a group to another thing in another group
▪ There was a one-to-one correspondence between the number of times the bell rang and the number of times the dog barked.
▪ We had a one-to-one meeting.
▪ There was a one-to-one correspondence between the number of times the bell rang and the number of times the dog barked.
— one–to–one adverb
▪ a mentor who advises one-to-one and in groups
▪ a mentor who advises one-to-one and in groups
