This Definition

thĭs

these

pronoun

The person or thing mentioned or understood.

This is John; this tastes good.

Webster's New World

Used to refer to what is about to be said.

Now don't laugh when you hear this.

American Heritage

The thing that is nearer than another referred to as “that”

This is larger than that.

Webster's New World

The less remote in thought of two contrasted things.

Of the two possibilities, this is more likely than that.

Webster's New World

Used to refer to the present event, action, or time.

Said he'd be back before this.

American Heritage

Synonyms:

Synonyms:
the thing indicated
this person
this-one
the-one
the aforementioned one
the one in question

adjective

Designating the person or thing mentioned or understood.

This man was John; this pie tastes good.

Webster's New World

Being nearer or more immediate.

This side and that side.

American Heritage

Designating the thing that is nearer than the one referred to as “that”

This desk is smaller than that one.

Webster's New World

Designating something that is being, or is about to be, mentioned, presented, etc.

Hear this song; this fact will convince you.

Webster's New World

Designating the less remote in thought of two contrasted things.

Of the two, this possibility is more likely than that.

Webster's New World

adverb

To this extent; so.

It was this big.

Webster's New World

determiner

The (thing) here (used in indicating something or someone nearby).

This classroom is where I learned to read and write.

Wiktionary

The known (thing) (used in indicating something or someone just mentioned).

They give the appearance of knowing what they're doing. It's this appearance that lets them get away with so much.

Wiktionary

The known (thing) (used in indicating something or someone about to be mentioned).

When asked what he wanted for his birthday, he gave this reply: “[...]"

Wiktionary

A known (thing) (used in first mentioning a person or thing that the speaker does not think is known to the audience). Compare with "a certain ...".

I met this woman the other day who's allergic to wheat. I didn't even know that was possible!

There's just this nervous mannerism that Bob has with his hands, and it drives me crazy.

Wiktionary

(Of a unit of time) Which is current.

It snowed this week.

Wiktionary

noun

(philosophy) Something being indicated that is here; one of these.

Wiktionary

interjection

(Internet slang) Indicates the speaker's strong approval or agreement with the previous material.

Wiktionary

Other Word Forms of This

Noun

Singular:

this

Plural:

these, thises

Origin of This

Middle English, from Old English þis (neuter demonstrative), from North Sea Germanic base *þa-, from Proto-Germanic *þat, from Proto-Indo-European *tód, extended form of demonstrative base *to-; + North Sea Germanic definitive suffix -s, from Proto-Indo-European *só (“this, that").

From Wiktionary
Middle English from Old English to- in Indo-European roots

From American Heritage Dictionary of the English Language, 5th Edition