infancy

As a noun infancy

is the earliest period of childhood (crawling rather than walking).

As an adjective undefined is

lacking a definition or value.

As nouns the difference between infantry and infancy

is that infantry is soldiers who fight on foot (on land), as opposed to cavalry and other mounted units, regardless of external transport (e.g. airborne) while infancy is the earliest period of childhood (crawling rather than walking).

As nouns the difference between infancy and maturity

is that infancy is the earliest period of childhood (crawling rather than walking) while maturity is the state of being mature, ready or ripe.

As nouns the difference between infancy and newborn

is that infancy is the earliest period of childhood (crawling rather than walking) while newborn is a recently born baby.

As an adjective newborn is

recently born.

As nouns the difference between baby and infancy

is that baby is baby (infant) while infancy is the earliest period of childhood (crawling rather than walking).

As nouns the difference between immaturity and infancy

is that immaturity is youth; the condition of being immature or not fully grown while infancy is the earliest period of childhood (crawling rather than walking).

As nouns the difference between inauguration and infancy

is that inauguration is the act of inaugurating, or inducting into office with solemnity; investiture by appropriate ceremonies while infancy is the earliest period of childhood (crawling rather than walking).

Physicaldevelopment is likely misspelled.

Physicaldevelopment has no English definition.

As a noun infancy is

the earliest period of childhood (crawling rather than walking).

Commencement is a related term of infancy.

As nouns the difference between commencement and infancy

is that commencement is the first existence of anything; act or fact of commencing; rise; origin; beginning; start while infancy is the earliest period of childhood (crawling rather than walking).

Initiation is a related term of infancy.

As nouns the difference between initiation and infancy

is that initiation is the act of initiating, or the process of being initiated or introduced; as, initiation into a society, into business, literature, etc while infancy is the earliest period of childhood (crawling rather than walking).