1 idol

1 incidentally

2 occasional

3 occasionally

4 by chance

5 randomly

1 occasionally

2 once in a while

3 sometimes

1 a chance encounter

2 to meet accidentally

1 to pair up

2 to match

3 to arrange in pairs

4 to add sth into a group

1 to do sth once in a while (idiom)

2 to do sth more as an exception than the rule

1 chance remarks can lead to public execution (idiom)

1 not alone but in pairs (idiom, usually derog.); not a unique occurrence

2 it's not the only case

1 too rich to be a good match (in marriage) (idiom)