The singular form is feed, a non-count noun; individual units are tons of feed, sacks of feed, trays or troughs of feed, etc. The only plural form for the noun feed is for types of feeds, such as cattle feed, chicken feed, etc. For example:
We have a shed where feeds are stored.
The word feed is also a verb: feed, feeds, feeding, fed.
The singular form of feet is foot.
The singular form is hilum.
The form plumber is the singular form; the plural form is plumbers.
The noun grandmother is the singular form.
The singular form would be majesty.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of feet is foot.
The singular form of "hypothysis" is "hypothesis."
The singular form is ombudsman.
it is already in its singular form.
The singular form is hilum.
The singular form is money.
The singular form of "cuffs" is cuff.
The singular form in stimulus.
The singular form for the plural noun stories is story.
The singular form for the noun families is family. The singular possessive form is family's.
The form plumber is the singular form; the plural form is plumbers.