The plural of fox is foxes.
.
The singular possessive form is foot's.
The plural of the noun knife is knives.
The plural possessive form is knives'
Example: These knives' maker is a master craftsman.
fixtures
The irregular plural possessive for foot is feet's.
Yes, 'understanding' is an abstract noun, a word for an emotion, knowledge, or belief. Understanding has no physical presence.
The word sheep is one of a handful in the English language in which the singular and plural forms are exactly the same. Sheep in plural form is just sheep.
The singular possessive form is sheep's.
The plural possessive form is sheep's.
For example: "a sheep's fleece" and "five sheep's fleeces".
Example sentences:
The sheep's owner sold it for a good price.
The sheep's owner sold them for a good price.
The singular possessive form for the noun army is army's.
knowledge
The plural form for the noun army is armies. The plural possessive form is armies'.
The singular possessive form for 'the tail of the fox' is the fox's tail.
The possessive form of the singular noun veto is veto's.
Example: A veto's power carries only the weight of one vote.
Knife's