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 singular form would be majesty.
The noun grandmother is the singular form.
The singular form of the demonstrative pronoun 'these' is this.
The singular form of "that" is "it."
The singular form is cuff.
it is already in its singular form.
"Stratum" is the singular form of stratum. The plural form is "strata".
The form hypothesis is the singular form. The plural form is hypotheses.
A singular form of dice is a die
The singular form of feet is foot.
The singular form of Oases is, Oasis.
"Wash" is the singular form of "wash."
The singular form of chromosomes is a chromatid.
A pair of scissors is the singular form.