In To vs. Into — What's the Difference?

"In" is an adverb; "to" prepositions the next part.

Indicates transformation or change in state.

"In" indicates a position; "to" introduces a purpose.

Preposition showing direction or movement.

"In" is a part of a verb phrase; "to" begins the next phrase.

Suggests involvement or interest.

"In" completes the action of a verb; "to" starts another phrase.

Refers to divisions or segments.

"In" denotes a state; "to" introduces direction.

Denotes a point in time.

To the inside or interior of

To the activity or occupation of

To the condition, state, or form of

So as to be in or be included in

(Informal) Interested in or involved with

To a point within the limits of a period of time or extent of space

In the direction of; toward

Against

As a divisor of

To or towards the inside of.

To or towards the region of.

Against, especially with force or violence.

Indicates transition into another form or substance.

Indicates division or the creation of subgroups or sections.

After the start of.

(colloquial) Interested in or attracted to.

Expressing the operation of multiplication.

(mathematics) Expressing the operation of division, with the denominator given first. Usually with "goes".

Investigating the subject (of).

To the inside of; within. It is used in a variety of applications.

Expressing entrance, or a passing from the outside of a thing to its interior parts; - following verbs expressing motion; as, come into the house; go into the church; one stream falls or runs into another; water enters into the fine vessels of plants.

Expressing penetration beyond the outside or surface, or access to the inside, or contents; as, to look into a letter or book; to look into an apartment.

Indicating insertion; as, to infuse more spirit or animation into a composition.

Denoting inclusion; as, put these ideas into other words.

Indicating the passing of a thing from one form, condition, or state to another; as, compound substances may be resolved into others which are more simple; ice is convertible into water, and water into vapor; men are more easily drawn than forced into compliance; we may reduce many distinct substances into one mass; men are led by evidence into belief of truth, and are often enticed into the commission of crimes; she burst into tears; children are sometimes frightened into fits; all persons are liable to be seduced into error and folly.

"Into" typically indicates motion, transformation, or direction.

No, they have distinct grammatical roles and meanings.

Yes, "Into" is a single preposition.

"She checked in to her flight online."

No, if "Into" is the correct term, separating it will change the sentence's meaning.

"She walked into the room."

Yes, "tune in" is a verb phrase, and "to" starts the next phrase, as in "tune in to the radio".

Use "In To" when "in" ends a verb phrase and is followed by a phrase starting with "to".

No, it can also indicate transformation or interest, like "turning into" or "being into" something.

If "in" and "to" can stand separately without changing meaning, it's "In To". If not, it's "Into".