"Woman Work" depicts women's unpaid labor as a form of slavery. Slaves by definition are dispossessed of the right to own anything. The poem's word choice and imagery are carefully deployed to show how and why the woman can call only the stars and the moonlight her own.
In the first stanza, the speaker lays out a litany of chores that are typically associated with women's physical and emotional labor: childcare, grocery shopping, cooking, serving food, sewing, housecleaning, tending the sick, etc.:
I've got the children to tend
The clothes to mend
The floor to mop
The food to shop
Then the chicken to fry
The baby to dry
I got company to feed
The garden to weed
I've got shirts to press
The tots to dress
The cane to be cut
I gotta clean up this hut
Then see about the sick
And the cotton to pick.
Yet in no case does the speaker claim that these tasks are personal to her. She does not speak of tending her children, just the children. She presses shirts, not her shirts. She cleans this hut, not her hut. The use of articles or demonstrative adjectives instead of the possessive adjective my suggests that Angelou's speaker represents not only one specific woman who is enumerating the tasks she has to undertake through her day, but "woman work" in general. This is the burden society places on all women, expecting them to do unpaid labor as a matter of course.
The last listed task, the cotton to pick, stands out from the rest. By including this in the list, Angelou achieves two ends. First, she dismantles the distinction between housework and paid employment and shows that it is artificial, not natural. Women from white-collar or landed-property families might have the luxury, or until fairly recently even the expectation, of devoting themselves solely to housework. But for working-class women, particularly women of color, employment has always been a necessity. Even if they have their own homes and children to look after, they have to work for money. In many cases, they are paid for the same tasks outside the home that they would do for free within their families: childcare, cleaning, nursing, etc.
Since the speaker has not said that she is caring for her own children, ironing her own shirts, etc., the poem shows that nothing inherent to these tasks makes them unworthy of payment. By connecting these tasks to picking cotton, which would in fact typically entail receiving wages nowadays, Angelou causes us to rethink our assumptions about the economic value of women's work. Further, picking cotton is not a gender-specific task, which also prompts the reader to question the blithe assumption that the other tasks are.
More trenchantly, in American history picking cotton is associated with slave labor. Slaves were forced to labor unpaid, and we expect women's work to be unpaid. Angelou depicts the burden of emotional and physical labor imposed on women as a form of slavery. Slaves of course had no property of their own. They did not even own their bodies, or have any claim to their children. The careful avoidance of the possessive adjective thus leads up to this depiction of women's work as a form of slavery.
As a slave, the speaker of course does not own anything else. The only things that are hers are those that belong to all humankind: natural features and phenomena like the rain, the ocean, and the sun. The movement from the highly particularized list of tasks in the first stanza to the universalized images of the conclusion reinforces that this condition of slavery is not something that is restricted to the particular woman who speaks this poem, but is common to women in general.