Editing Minyan (section)

=== People who join the minyan: ===
Only adult Jewish men (who have reached the age of mitzvos) who are obligated in mitzvos join the minyan. A shoteh (mentally incompetent person), a cheresh who cannot hear and cannot speak (meaning one who lacks understanding and is exempt from mitzvos), and a katan (minor) do not join the minyan. Similarly, in exceptional cases, there are people whom halacha determines cannot join a minyan, such as someone who is under niduy (excommunication) or a sinner and the like.

Likewise, a woman cannot be included in a men's minyan for reasons of tznius and because of kvod hatzibur (honor of the congregation).

For Birchas Hazimon with ten people during Birchas Hamazon, there is an additional reason why women do not join, which is because of the halachic principle that in order to fulfill someone else's obligation, the one fulfilling it must be obligated at the same level. Since men are obligated in Birchas Hamazon from the Torah (d'oraisa), and women from the Rabbis (d'rabbanan), women cannot fulfill the obligation of men in Birchas Hamazon.