one-on-one
adjective (North American English)(also one-to-one especially in British English)
[usually before noun]between two people only 一对一的；仅限两人之间的 a one-on-one meeting 一对一的会议
matching something else in an exact way 一一对应的；完全对应的 There is no one-on-one correspondence between sounds and letters. 声音和字母之间没有一对一的对应关系。