Ummah is derived from the two letter Arabic root noun Aleph Meem, which translate to mother. One can think of Ummah as the mother people from an Islamic point of view.

Ummah ( Om-mah ), mother people. Aleph Meem Ha.

It also means his mother, but it depends on the context of the sentence.

Further variation of Aleph Meem:

Ummi ( Om-me), my mother. Aleph Meem Ya.

Ummoh (Om-moh ), his mother. Aleph Meem Ha.

Ummaha (Om-ma-ha), her mother. Aleph Meem Ha Aleph.

Ummahatana (Om-ma-ha-to-na), our mothers. Aleph Meem Ha Ta Noon Aleph.

The letter Aleph sounds like an O sound because of the accent mark attachment of a small Wow letter, called a dammah, over the Aleph. Meem is doubled by adding a shaddah accent mark.

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Occourence of Ummah in the Qur'an:

To every ummah (was sent) a Messenger: when their Messenger comes (before them), the matter will be judged between them with justice, and they will not be wronged. (10:47)

Mankind was but one ummah, but differed (later). Had it not been for a Word that went forth before from thy Lord, their differences would have been settled between them. (10:19)

Mankind was one single ummah. And Allah sent Messengers with glad tidings and warnings; and with them He sent the Book in truth, to judge between people in matters wherein they differed; but the People of the Book after the clear Signs came to them, did not differ among themselves, except through selfish contumacy. Allah by His Grace guided the Believers to the Truth, concerning what wherein they differed. For Allah guides whom He will to a path that is straight. (2:213)

Thus have We made of you an Ummah justly balanced. That you might be witnesses over the nations, and the Messenger a witness over yourselves; and We appointed the Qibla to which you were used, only to test those who followed the Messenger from those who would turn on their heels (from the Faith). Indeed it was (a change) momentous, except to those guided by Allah. And never would Allah make your faith of no effect, for Allah is to all people most surely full of Kindness, Most Merciful. (2:143)

If Allah so willed, He could make you all one Ummah: but He leaves straying whom He pleases, and He guides whom He pleases: but you shall certainly be called to account for all your actions. (16:93)

And verily this Ummah of yours is One Ummah and I am your Lord and Cherisher: therefore fear Me (and no other). (23:52)