erstwhile

As adjectives the difference between erstwhile and undefined

is that erstwhile is (literary|legal) former, previous while undefined is lacking a definition or value.

As an adverb erstwhile

is formerly; in the past.

As adverbs the difference between erstwhile and before

is that erstwhile is formerly; in the past while before is at an earlier time.

As an adjective erstwhile

is (literary|legal) former, previous.

As a preposition before is

earlier than (in time).

As a conjunction before is

in advance of the time when.

As adverbs the difference between erstwhile and yester

is that erstwhile is formerly; in the past while yester is yesterday.

As adjectives the difference between erstwhile and yester

is that erstwhile is former, previous while yester is last; last past; next before; of or pertaining to yesterday.

As a noun yester is

yesterday.

As adjectives the difference between executive and erstwhile

is that executive is while erstwhile is (literary|legal) former, previous.

As an adverb erstwhile is

formerly; in the past.

As adjectives the difference between erstwhile and defunct

is that erstwhile is (literary|legal) former, previous while defunct is deceased, dead.

As an adverb erstwhile

is formerly; in the past.

As a verb defunct is

to make defunct.

As a noun defunct is

the dead person (referred to).

Erstwhile is a synonym of bygone.

As adjectives the difference between erstwhile and bygone

is that erstwhile is (literary|legal) former, previous while bygone is having been or happened in the far past.

As an adverb erstwhile

is formerly; in the past.

As a noun bygone is

a person or occurrence that took place in the past.

Earlier is a synonym of erstwhile.

As adverbs the difference between erstwhile and earlier

is that erstwhile is formerly; in the past while earlier is comparative of early.

As adjectives the difference between erstwhile and earlier

is that erstwhile is former, previous while earlier is comparative of early.

As a noun taxonomy

is the science or the technique used to make a classification.

As an adverb erstwhile is

formerly; in the past.

As an adjective erstwhile is

former, previous.

As adverbs the difference between erstwhile and umwhile

is that erstwhile is formerly; in the past while umwhile is formerly; late; whilom.

As adjectives the difference between erstwhile and umwhile

is that erstwhile is former, previous while umwhile is erstwhile; late; former.