143. The "Blood" Radical: 血
If you've ever sliced open a finger while preparing food, you know that "dish" and "blood" aren't so far apart. The same goes for these two kanji:
皿 (1307: dish, plate; a helping)
血 (270: blood)
Each shape doubles as a radical:
皿 (radical 108: "dish")
血 (radical 143: "blood")
Given that these differ by only a dot, it makes sense that the nickname "dotted dish" distinguishes 血 from 皿. But the official English name for radical 143 is "blood."
The blood kanji 血 carries the Joyo kun-yomi ち, which is the primary radical name in Japanese. It works for each of the Joyo kanji featuring this on-duty radical:
血 (270: blood)
衆 (705: the public; crowd; many)
The six-stroke 血 radical has no variants. As you can see, it retains its shape (but becomes shorter) when crowning a kanji, as in 衆.
If 血 occupies the left side of a character, the radical name becomes ちへん. (To understand this nomenclature, go to Radical Terms, see the "Radical Positions" section, and read about Position 1, -へん.) That radical name works for these non-Joyo kanji in which 血 is on duty:
衂 (nosebleed)
衄 (nosebleed)
These characters are variants of each other. I love that there's even one kanji for a nosebleed, much less two! The first almost makes sense to me, combining "blood" with 刃 (blade; sword). But the second? I'm scratching my head because the non-Joyo 丑 can represent a zodiacal ox! Ah, Kanjigen says that in this case the 丑 originally meant "to bend one's hand (fingers) and grasp (something)," evolving to mean "soft and sticky" and making 衄 represent "sticky, soft nosebleed"!
Photo Credit: Eve Kushner
Etymologies
I mentioned that blood and dishes aren't far apart conceptually, but let's see how that holds up etymologically:
血 (270: blood)
Henshall says in his newer edition that this character shows a bowl (皿) with blood in it (the dot), representing "a pledge." Later, 血 came to mean just "blood."
衆 (705: the public; crowd; many)
This shape bears no connection to blood. According to Henshall, the upper component may have meant "eye."
Photo Credit: Eve Kushner