No, it's a logical for you statement that you have grown hearing that and with that logic, but mathematicians have another opinion. They defined majority and plurality different.
Here is how:

We have a large group of N different teams/smaller groups.
Ans we know that
team-1 counts X1 members in the group,
team-2 counts X2 members in the group,
.....................
..................
...
team-N counts XN members in the group.

And that TotX = X1 + X2 + ... + XN

Then we say that: team-G is the majority of the whole group if and only if XG > (TotX-XG)

Also we say that: team-G is the plurality of the whole group if and only if for every K from 1 to N except G, is true that XG > XK