Radical 1

Radical 1 or radical one meaning "one" is one of the 6 Kangxi radicals composed of 1 stroke. It is the simplest Chinese character in the language due to consisting of only one line.
In the Kangxi Dictionary, there are 60 characters to be found under this radical.
一 is also the 1st indexing component in the Table of Indexing [Chinese Character Components] predominantly adopted by Simplified Chinese dictionaries published in mainland China.

Derived characters

Strokes	Characters
+0
+1
+2	^SC/^JP
+3	^SC/JP/^TC ^SC
+4	^SC ^SC ^SC ^SC
+5	^JP
+6	^SC ^SC
+7	^SC

In calligraphy

The only stroke in radical one, known as 橫/横 héng "horizontal", is called 策 cè in the eight principles of the character 永 which are the basis of Chinese calligraphy.

Sinogram

As an isolated character it is one of the Kyōiku kanji or Kanji taught in elementary school in Japan. It is a first grade kanji.