עליות, aliyot; "ascent" or "going up") is the calling of a member of a Jewish congregation up to the bimah for a segment of the formal Torah reading.
[1] The Torah reading consists of a series of aliyot: three on normal weekdays, seven on Shabbat, and other numbers on holidays.
In Yemenite communities, the oleh reads the portion themself, while another person, usually a young boy, recites the Targum after each verse.
[4] Orthodox Judaism recognizes limited exceptions from the general principle that a Kohen is called first.
For example, there are cases where calling a kohen first would prevent individuals celebrating special occasions from each having an aliyah.
Reform and Reconstructionist Judaism consider halakhah no longer binding and believe the entire ancient sacrificial system to be incompatible with modern sensibilities.
On Saturday mornings, there are seven olim, the maximum of any day, but more may be added if desired, by subdividing these seven aliyot or repeating passages (according to the custom of some communities).
Bet Yoseph quotes a geonic source in explanation of this number (Ein Pochasim, Tur, Hilchot Shabbat 282).
The seven benedictions correspond to the seven voices of God (kol) mentioned in the Twenty-ninth Psalm and again in connection with the giving of the Torah (beginning with Exodus 19:16, Midrash Yelamdenu).
In the late 12th and early 13th century, Rabbi Meir of Rothenburg ruled that, in a community consisting entirely of kohanim, the prohibition on calling kohanim for anything but the first two and maftir aliyot creates a deadlock situation which should be resolved by calling women to the Torah for all the intermediate aliyot.
In 1955, the Committee on Jewish Law and Standards authorized women to have an aliyah at Torah-reading services.
[5] In order to practice social distancing to limit the number of individuals on the bimah as congregations reopened during 2020 in later stages that year of the COVID-19 pandemic, Orthodox Union guidelines suggested that the person reading the Torah take all three aliyot.