Osanai is the Japanese word for ‘childish’, explained

What does “osanai” mean in Japanese?

Native speakers say “osanai” to mean ‘childish’ or just ‘very young’ in Japanese. Perhaps, some Japanese learners know this word as it is sometimes used in Japanese movies, songs, novels, manga, anime, and the like. In this blog post, however, I will explain this word together with its major conjugations. And also, I will explain how to use them through example sentences. My explanations would help Japanese learners use “osanai” more properly. Then, let’s get started!

Contents

• Definition and meanings of “osanai”
  • Example #1: how to say “childish” in Japanese
• Osanakunai: the nai form of “osanai”
  • Example #2: how to say “not childish” in Japanese
• Osanakatta: the ta form of “osanai”
  • Example #3: how to say “was childish” in Japanese
• Osanakute: the te form of “osanai”
  • Example #4: how to say “childish and” in Japanese
• Osanakereba: the ba form of “osanai”
  • Example #5: how to say “if very young” in Japanese
• Summary

Definition and meanings of “osanai”

Let me start with the definition and meanings of “osanai”.

• osanai – 幼い (おさない) : an i-adjective meaning ‘childish’ or just ‘very young’ in Japanese.

Japanese native speakers use this i-adjective to describe someone who is not yet fully grown physically or mentally.

The definition and meanings are simple and clear, I think. Then, let me explain how to use this i-adjective through the example sentence below.

Example #1: how to say “childish” in Japanese

Below are the new words used in the example sentence.

• kanojo – 彼女 (かのじょ) : a pronoun meaning ‘she’ in Japanese.
• no – の : a case particle used after a noun or pronoun to make its possessive case. In the example, this is used after “kanojo” to make its possessive case, “kanojo no”, which means ‘her’ in Japanese.
• furumai – 振る舞い (ふるまい) : a noun meaning ‘behavior’ in Japanese.
• wa – は : a binding particle working as a case marker or topic marker. In the example, this works after “kanojo no furumai” to make the subject in the sentence.

This is a typical usage of “osanai”. In this example, it works as the complement in the sentence. Like other adjectives, however, it can also work as a modifier in front of a noun. For example, we can say “osanai furumai” to mean ‘childish behavior’. It’s worth knowing, I think.

So far, I’ve explained the definition and meanings of “osanai” and how to use it through the example sentence. In the rest part of this blog post, I will explain its major conjugations. The first one is “osanakunai”.

Osanakunai: the nai form of “osanai”

Below are the definition and meanings of “osanakunai”.

• osanakunai – 幼くない (おさなくない) : the nai form of “osanai”, which means ‘not childish’ or ‘not very young’ in Japanese.

Grammatically, “osanakunai” consists of the following two parts:

• osanaku – 幼く (おさなく) : one conjugation of “osanai”. This can have a smooth connection with “nai”.
• nai – ない : an auxiliary verb used after a verb, adjective, or auxiliary verb to deny its meaning. Word orders in Japanese and English are different, but the role of this auxiliary verb is similar to that of “not”.

From these two parts, we can understand that “osanakunai” is literally the nai form of “osanai” and means ‘not childish’ or ‘not very young’ in Japanese. Then, let me explain how to use this form through the example sentence below.

Example #2: how to say “not childish” in Japanese

Below is the new word used in the example sentence.

• imouto – 妹 (いもうと) : a noun meaning ‘little sister’ in Japanese. This can also work as plural. Learn more about Japanese plural.

This is a typical usage of “osanakunai”. When we want to mean ‘not childish’ in Japanese, this nai form is a good option.

Osanakatta: the ta form of “osanai”

Below are the definition and meanings of “osanakatta”.

• osanakatta – 幼かった (おさなかった) : the ta form of “osanai”, which means ‘was childish’, ‘was very young’, or such in Japanese.

Grammatically, “osanakatta” consists of the following two parts:

• osanakat – 幼かっ (おさなかっ) : one conjugation of “osanai”. This can have a smooth connection with “ta”.
• ta – た : an auxiliary verb used after a verb, adjective, or auxiliary verb to make its past tense form. Probably, this is well known as a part of Japanese ta form.

From these two parts, we can understand that “osanakatta” is literally the ta form of “osanai” and means ‘was childish’, ‘was very young’, or such in Japanese. Let me explain how to use this form through the example sentence below.

Example #3: how to say “was childish” in Japanese

Below are the new words used in the example sentence.

• kareshi – 彼氏 (かれし) : a pronoun meaning ‘boyfriend’ in Japanese.
• mo – も : a binding particle making the subject word or the object word in a sentence with adding the meaning of ‘too’, ‘also’, or ‘as well’. In the example, this works after “kanojo no kareshi no furumai” to make the subject in the sentence with adding the meaning of ‘too’.

This is a typical usage of “osanakatta”. When we want to use the past tense form of “osanai”, this ta form is the best option.

Osanakute: the te form of “osanai”

Below are the definition and meanings of “osanakute”.

• osanakute – 幼くて (おさなくて) : the te form of “osanai”, which means ‘childish’ or ‘very young’ in Japanese.

Grammatically, “osanakute” consists of the following two parts:

• osanaku – 幼く (おさなく) : one conjugation of “osanai”. This can have a smooth connection with “te”.
• te – て : a conjunctive particle used after a verb, adjective, or auxiliary verb to make its te form.

From these two parts, we can understand that “osanakute” is literally the te form of “osanai”. In Japanese, te-formed words have some important roles. One of them is make smooth connections of words. So, “osanakute” is very useful when we want to use “osanai” in front of another adjective, a verb, or an auxiliary verb. Let me explain this usage through the example sentence below.

Example #4: how to say “childish and” in Japanese

Below is the new word used in the example sentence.

• uzai – ウザい (うざい) : an i-adjective meaning ‘annoying’ or such in Japanese.

This is a typical usage of “osanakute”. In the example, it has the smooth connection with “uzai”. When we want to use “osanai” in front of another adjective like this, its te form is very useful to make a smooth connection.

Osanakereba: the ba form of “osanai”

Lastly, let me explain the definition and meanings of “osanakereba”.

• osanakereba – 幼ければ (おさなければ) : the ba form of “osanai”, which makes a conditional clause in a sentence with meaning ‘childish’ or ‘very young’ in Japanese.

Grammatically, “osanakereba” consists of the following two parts:

• osanakere – 幼けれ (おさなけれ) : one conjugation of “osanai”. This can have a smooth connection with “ba”.
• ba – ば : a conjunctive particle used after a verb, adjective, or auxiliary verb to make its ba form.

From these two parts, we can understand that “osanakereba” is literally the ba form of “osanai”. In Japanese, the ba forms of words can work as their conditional forms. So, we can use “osanakereba” to make a conditional clause in a sentence with adding the meaning of ‘childish’ or ‘very young’. Let me explain this usage through the example sentence below.

Example #5: how to say “if very young” in Japanese

Below are the new words used in the example sentence.

• kodomo – 子供 (こども) : a noun meaning ‘child’ or ‘kid’ in Japanese. This can also work as plural.
• ga – が : a case particle used to make the subject word or the object word in a sentence. In the example, this is used after “kodomo” to make the subject in the conditional clause.
• mada – まだ : an adverb meaning ‘still’ in Japanese.
• kono – この : a determiner used before a noun referring to a thing close to the speaker. In the example, this is used before “hon” to say “this book” in Japanese.
• hon – 本 (ほん) : a noun meaning ‘book’ in Japanese. This can also work as plural.
• wo – を : a case particle used to make the object word in a sentence. In the example, this is used after “hon” to make the object in the second clause.
• susume – 薦め (すすめ) : one conjugation of the verb, “susumeru”, which means ‘to recommend’ in Japanese. In the example, it has been conjugated for the better connection with its following word.
• masu – ます : an auxiliary verb used after a verb to make it polite. Probably, this is well known as a part of Japanese masu form. In the example, this is used after “susume” to make it sound polite.

This is a typical usage of “osanakereba”. In this example, it works as a part of the conditional clause, “kodomo ga mada osanakereba”, which means ‘if your kids are still very young’ in Japanese. When we want to make a conditional clause in a sentence with adding the meaning of ‘childish’ or ‘very young’, this ba form is a good option.

Summary

In this blog post, I’ve explained the definition and meanings of “osanai” together with its major conjugations. And also, I’ve explained how to use them through the example sentences. Let me summarize them as follows.

• osanai – 幼い (おさない) : an i-adjective meaning ‘childish’ or just ‘very young’ in Japanese. This can work as both a modifier and a complement.
• osanakunai – 幼くない (おさなくない) : the nai form of “osanai”, which means ‘not childish’ or ‘not very young’ in Japanese.
• osanakatta – 幼かった (おさなかった) : the ta form of “osanai”, which means ‘was childish’, ‘was very young’, or such in Japanese.
• osanakute – 幼くて (おさなくて) : the te form of “osanai”, which means ‘childish’ or ‘very young’ in Japanese. When we want to use “osanai” in front of another adjective, this te form is very useful to make a smooth connection.
• osanakereba – 幼ければ (おさなければ) : the ba form of “osanai”, which makes a conditional clause in a sentence with meaning ‘childish’ or ‘very young’ in Japanese.

Hope my explanations are understandable and helpful for Japanese learners.