Many radical have meaning, but not all.
亅 is both a radical and a stroke. In Chinese, like English, all strokes are meaningless. You cannot say strokes c and | in the English letter d have a specific meaning.
Radical is called “indexing component” (部首) in China’s national standard GF 0011-2009. In this standard, there are 201 indexing components in Simplified Chinese. In pp. 3-5 of GF 0011-2009, we can see Indexing Component No 2 is 丨 (alternative form 亅) which is a single stroke and does not have any meaning. However Indexing Component No 22 刀 is a complete character means knife, as it mentioned, ⺈ and 刂 are 刀’s alternative form.
Therefore, we know that indexing component could be a complete character or some stroke(s), including alternative forms such as 亅 and ⺈. But why we need to recognise indexing components? Let us talk about China’s dictionaries (Chinese-Chinese) and Chinese learner's dictionaries (Chinese-English / Chinese-French / Chinese-Arabic…) in paper form. These dictionaries usually arrange their pages by Pinyin A-Z. So if you know Pinyin pronunciation, you can easily locate the pages by ABCD … XYZ Latin alphabet, just like what you do in English or French dictionaries. However, what if you do not know the pronunciation of a character? You can use indexing components to look up a character.
Let's say you do not know how to pronounce 分, and you want to look it up in a dictionary. I have a dictionary for native speakers called Contemporary Chinese Dictionary (《现代汉语词典》) 7th edition. I will use it as an example.
- Turn to indexing component directory (部首目录) page of the dictionary.
- Guess the indexing component maybe No 11 八. It says it is on directory page 17 (page number of preface, not main entries).
- Turn to directory page 17. It shows all characters containing indexing component of 八. 380 386
- Count the stroke number of the rest part of the character (indexing component excluded), i.e. rest part of 分 is the part which does not contain 八, that is 刀. Therefore, the stroke number of 刀 is 2.
- Locate the title “2 strokes (left)” under the indexing component, then it says 分 is on pp. 380 and 386.
- Turn to main entries:
- p. 380 分 (fēn) <1> v. sperate 分离 <2> v.distribute 分配 … <8> measure word. unit in currency and time etc …
- p. 386 分 (fèn) <1> n. ingredient 成分 …
- Most indexing component has a name, appendix of Contemporary Chinese Dictionary (7th ed) shows these names. ⺈ is called 斜刀头 (xiédāotóu). If you learn Chinese calligraphy, you will know that the stoke 丨 is called 竖 (shù) and 亅 is called 竖钩 (shùgōu).
- The indexing component of 分 should be 八. However, to reduce learners’ workload, if learners look up indexing component 刀, they can also see 分 present (with a ° mark denotes 刀 is not recommended for 分).
- Traditional Chinese uses Kangxi Radicals (total 214 radicals), which is the origin of GF 0011-2009. Traditional Chinese dictionaries in Taiwan usually order the characters by Bopomofo (注音|zhùyīn) such as ㄅ (b in Pinyin), ㄆ (p in Pinyin), ㄇ (m in Pinyin), ㄈ (f in Pinyin). Cantonese dictionaries usually order the characters by Jyutping (粵拼|yuèpīn), which is a phonetic alphabet in Latin script (A-Z) designed for Cantonese.