A
Japanese phrase particle, similar to
wa but without any
contrastive function.
Ga is used like
wa, but places the
emphasis on the
word(s) it modifies. For example...
Ano hito wa nihon-jin desu
That person is Japanese (as opposed to American, French, etc).
Ano hito ga nihon-jin desu
That person is Japanese (he is the one who is Japanese, not someone else).