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## Main Question or Discussion Point

Hello, I've got difficulties in understanding what is the point group a o crystal. I read that it is the subset of symmetry operations leaving at least one point of the lattice fixed. But I do not understand:

1) This point must be the same for all the members of the point group?

2) if it must be the same, then the definition is point dependent?

3) if it must not be the same, then how can we say that composition of two elements of the point group is still a member of the point group?

Thanks a lot for any help,

Tirrel

1) This point must be the same for all the members of the point group?

2) if it must be the same, then the definition is point dependent?

3) if it must not be the same, then how can we say that composition of two elements of the point group is still a member of the point group?

Thanks a lot for any help,

Tirrel