Theory:

When a noun is formed by adding root word to a verb or adjective is called Noun formation.
Example:
endure (verb) + ance (root word) = endurance (noun)
evident (adjective) + ance (root word) = evidence (noun)
What is a noun?
Nouns are words used for naming a person, place or a thing.
Example:
1. people
2. city
3. lion
Rules to be followed in noun formation 
Let's see how nouns are formed by adding -ance and -ence to a verb:
Rule:1 If a verb ends with -y, -ure, -ear then the noun form will end with -ance. If a verb ends with 'y' replace it with 'i' and add -ance to form a noun.
Example:
appear (verb) + ance (root word) = appearance (noun)
apply (verb) + (ance) (root word) = appliance (noun)
Rule:2 If a verb ends with -ere, then the noun formed will end with -ence.
Example:
adhere (verb) + ence (root word)= adherence (noun)
differ (verb) +ence (root word) = difference (noun)
Let's see how nouns are formed by adding -ance and -ence to a adjective:
Rule:3 If an adjective ends with -ant then the noun form will end with -ance.
Example:
distant (adjective) + ance (root word) = distance (noun)
important (adjective) + ance (root word) = importance (noun)
Rule:4 If an adjective ends with -ent, -ing then the noun form will end with -ence.
Example:
innocent (adjective) + ence (root word) = innocence (noun)
excellent (adjective) +ence (root word) = excellence (noun)
Examples of noun formation from the lesson "The Summit Within":
S.No
Words
Noun form
1
EndureEndurance
2
PersistPersistence
3
SignifySignificance
4
MaintainMaintenance
5
ConfideConfidence
6
AbhorAbhorrence