11. The "Enter" Radical: 入

The "enter" radical  is on duty in just one Joyo kanji, which is the 入 character itself:

入 (63: to enter, come in; put in; contain; accept; emphatic verbal suffix)

Henshall says in his newer edition that this shape depicts the "entrance to a dwelling." 

The Japanese Names of the 入 Radical 

The 入 kanji carries four Joyo yomi—namely, い•る, い•れる, はい•る, and ニュウ. Two have inspired names for the radical:



When the radical sits at the top of a character, 入 can also have these names: 



In both cases, the いり comes from いる. The かしら (頭), voiced as がしら in the radical name, means "top," and the やね (屋根) means "roof."

Though we have two names for 入 at the top of a character, I'm hard-pressed to find any examples of that situation!

The Shape of the "Enter" Radical

The shape of our two-stroke radical is quite simple. The only variable is that the 入 may have a hook on top, as in this sign:

Photo Credit: Lutlam

At Lake Haruna (榛名湖, はるなこ) in Gunma Prefecture on Honshu, this sign issues a prohibition:

Going on the Ice Is Not Permitted

氷上 (ひょうじょう: on ice); 立入 (たちいり:
entering); 禁止 (きんし: prohibition)

I found this 立入 strange, as no one would likely enter the ice. But the idea is that the frozen lake constitutes an area that one should not enter.

Alternatively, the hook may disappear, turning the radical into an inverted Y:

Photo Credit: Ulrike Narins

This sign is as straightforward as the font for these words:

登山道 (とざんどう: mountain trail; path up a mountain)

入口 (いりぐち: entrance)

The 入 Component in Other Kanji

The 入 component plays a role in this kanji, where the on-duty radical is 辶 ("movement"):

込 (1275: to move inward; emphatic verbal suffix; be crowded; including; concentrate on)

In the past, 入 also served as a component in the following character:

両 (411: both; car; old monetary unit) 

I'm referring to 兩, now the non-Joyo variant. Our radical showed up twice in that composition and has completely disappeared in the Joyo model! 

Similarly, 入 has vanished from the Joyo version of this kanji:

内 (364: inside, within; private, unofficial)

The character once consisted of 冂 + 入, and our radical was actually on duty then. But in 1981 the Joyo shape officially became 冂 + 人, with 冂 ("upside-down box") as the on-duty radical.

A Look-Alike Radical

The history of 内 brings up another point of interest—namely, that 入 has a look-alike radical:

人 ("person")