therein

As adverbs the difference between thereinto and therein

is that thereinto is (archaic) into that place, state etc while therein is (pronominal) in that; in him/her/it.

As adverbs the difference between therein and inside

is that therein is (pronominal) in that; in him/her/it while inside is within or towards the interior of something, especially a building.

As a noun inside is

the interior or inner or lesser part.

As a preposition inside is

within the interior of something, closest to the center or to a specific point of reference.

As an adjective inside is

originating from or arranged by someone inside an organisation.

As adverbs the difference between theretofore and therein

is that theretofore is until that time while therein is (pronominal) in that; in him/her/it.

As an adverb therein

is (pronominal) in that; in him/her/it.

As an adjective undefined is

lacking a definition or value.

As adverbs the difference between therein and therefrom

is that therein is in that; in him/her/it while therefrom is from that; from him, her, or it.

As adverbs the difference between therein and hereof

is that therein is (pronominal) in that; in him/her/it while hereof is of this.

As a conjunction whilst

is (british|rare or literary in north america) while, at the same time.

As an adverb therein is

(pronominal) in that; in him/her/it.

As adverbs the difference between hereunder and therein

is that hereunder is under this while therein is (pronominal) in that; in him/her/it.

As adverbs the difference between therein and thereupon

is that therein is (pronominal) in that; in him/her/it while thereupon is upon that/it, following that/it.

As an adverb therein

is in that; in him/her/it.

As a determiner her is

belonging to her.

As a pronoun her is

the form of she used after a preposition or as the object of a verb; that woman, that ship, etc.