【Japanese Grammar】Infinitive

Sentence pattern
Sentence pattern
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On this page, you can learn about Japanese Infinitive which is 不定詞(ふ・てい・し/fu te i shi)in Japanese.

Introduction

Here are examples of Infinitive. The basic format of Infinitive is ‘to + verb’.

  • I like to swim.
  • This is a pool to swim.
  • I go to pool to swim.

You can see ‘to swim’ in all the sentences but they work all in a different way.

Infinitive is divided into three groups, following how it works in a sentence.

They are:

  • Noun Infinitive,
  • Adjective Infinitive and
  • Adverb Infinitive.

Noun, Adjective and Adverb

Before learning Infinitive, let’s learn what noun, adjective and adverb are.

Noun

Noun is a name of a thing which can be tangible or intangible.

Example for tangible
  • girl
  • robot
  • tennis
  • salt
Example for intangible
  • beauty
  • sadness
  • friendship
  • environment

Adjective

Adjective is for describing a noun. It is often called ‘describing word’.

Example for adjective (bold ones below)
  • happy man
  • long boat
  • old house
  • something new

Adverb

Adverb is for describing a verb. Split the word ‘adverb’. You can see ‘ad (add)’ and ‘verb’. Adverb is a word, the meaning of which is added onto a verb.

Example for adverb (bold ones below)
  • run fast
  • study hard
  • eat slowly
  • enjoy responsibly

Noun Infinitive: to + verb = verb + こと

Noun Infinitive is ‘to + verb’ which is used as if it’s a noun. You can consider it Noun Infinitive if you replace it with ‘a thing‘ and it still makes sense.

Amongst the three sentences below, which ‘to swim’ can be replaced with ‘a thing’?

  • I like to swim.
  • This is a pool to swim.
  • I go to pool to swim.
  • I like a thing.
  • This is a pool a thing.
  • I go to pool a thing.

The first one makes sense, so that is Noun Infinitive. Let’s revise the sentence pattern:

Noun Infinitive: to + verb = verb + こと

Here is an example of how to translate Noun Infinitive:

I like to swim.

わたし は およぐこと がすきです。

Exercise

Task: Change into Japanese.

  • My mother likes to talk with friends.
  • My hobby is to play baseball.
  • It is important to go to school.
  • 母は友だちと話すことが好きです。
  • 私のしゅみはやきゅうをすることです。
  • 学校に行くことは大せつです。

Adverb Infinitive: to + verb = verb + ために

Adverb Infinitive is ‘to + verb’ which is used as if it’s an adverb. You can consider it Adverb Infinitive if you rewrite ‘to + verb’ with ‘because’ and it still makes sense.

Amongst the three sentences below, which ‘to swim’ can be written, using ‘because’?

  • I like to swim.
  • This is a pool to swim.
  • I go to pool to swim.
  • I like because I swim.
  • This is a pool because this swims.
  • I go to pool because I swim.

The third one makes sense, so that is Adverb Infinitive. Let’s revise the sentence pattern:

Adverb Infinitive: to + verb = verb + ために

Here is an example of how to translate Adverb Infinitive:

I go to pool to swim.

わたし は およぐために プール に いく。

Exercise

Task: Change into Japanese.

  • I go to Japan to study Japanese.
  • My older brother saved money to buy a car.
  • We came here to win a game.
  • 私は日本語を勉強するために日本に行きます。
  • 弟は車を買うためにお金をためました。
  • 私たちはしあいにかつためにここに来ました。

Adjective Infinitive: to + verb = verb + ための

Adjective Infinitive is ‘to + verb’ which is used as if it’s an adjective.

You can consider it Adjective Infinitive if you:

  • see it after a noun plus
  • can’t rewrite ‘to + verb’ using ‘because’.

Amongst the three sentences below, which ‘to swim’ meets the two conditions?

  • I like to swim.
  • This is a pool to swim.
  • I go to pool to swim.
  • I like because I swim.
  • This is a pool because I swim.
  • I go to pool because I swim.

‘to swim’ in the second and third sentence come after a noun.

However, the second one does not make sense when it is rewritten using ‘because’.

Therefore, the second ‘to swim’ is Adjective Infinitive.

Adjective Infinitive: to + verb = verb + ための

Here is an example of how to translate Adjective Infinitive:

This is a pool to swim.

これ は およぐ ための プール です。

Exercise

Task: Change into Japanese.

  • I want something to drink.
  • I don’t know what to do.
  • This is a tool to open a can.

The answer in a bracket is a literal translation which Japanese people would not say, but help you to understand the sentence pattern.

  • 私は飲みものがほしいです。(私は飲むための何かがほしいです。)
  • 私は何をしたらいいのかわかりません。(私はするためのことがわかりません。)
  • これはカンをあけるための道ぐです。

Extension: べき

べき should be sometimes used instead of ための for Adjective Infinitive.

Example

Japan has a lot of places to visit.

日本 には おとずれる べき たくさんの場所 があります。

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