In lang=en terms the difference between pair and tie
is that
pair is a pair of breasts while
tie is to unite (musical notes) with a line or slur in the notation.
In cricket terms the difference between pair and tie
is that
pair is a score of zero runs (a duck) in both innings of a two-innings match while
tie is the situation at the end of all innings of a match where both sides have the same total of runs (different to a draw).
In transitive terms the difference between pair and tie
is that
pair is to bring two (animals, notably dogs) together for mating while
tie is to secure (something) by string or the like.