The following six words can be grouped into nine pairs, when the pairs are joined in a certain way. Each pair is joined in the same way. Can you determine the link that will connect the words?

CAN
RAIN
BAR
MITE
LAUGH
RACE

HINT:
The link consists of the same three letters.

Answer:

canTERmite
can TERrace
canTERrain

barTERmite
barTERrace
barTERrain

laughTERmite
laughTERrace
laughTERrain