I was updating my iTalki profile, and discussed my 词汇量. I then thought, maybe I should also mention my "汉字量". It seems 汉字量 is not a word, though.
I guess it makes sense, 汉字量 is "quantity of hanzi", and doesn't necessarily refer to the hanzi you know. However, the same logic applies to 词汇量.
Question: If 词汇量 is a word, why is 汉字量 not a word?
This question is in fact asking how a compound word in the Chinese language is formed and used. A compound word includes multiple characters, each with its own basic meaning. Combining the characters in a certain order may reveal the meaning of the compound word.
However, the underlying logic of word analysis can not be applied inversely, because not any arbitrary two or more meaningful characters could be combined to form a meaningful compounded word, even if the apparent logic might suggest a meaningful word. For example, the word 物理 means physics, but 物论 or 物学 means nothing.
词汇 is the translation of "vocabulary", and 词汇量 is the number of words included in the vocabulary of a book or known by a person. 汉字 means a Chinese character or a collection of characters. But people do not use 汉字量 to indicate the quantity of 汉字 (s) included in a book or known by a person. I do not know why, but that is the current situation. It is possible that it become a word in the future.
Whenever you have a doubt, just Google it. When I Google 汉字量, I only get 汉语识字量。
By the way, 字数 (number of characters) is a specific word used in book publication.
「詞匯量」 is a size/quantity/measure (量) of (someone's) vocabulary (詞匯). Like the English word vocabulary, you speak of someone's vocabulary size (詞匯量) directly using the word 「詞匯」.
In English, you may also describe this as someone's knowledge of words or letters, but you would need to phrase it as how many words/letters they know, and not their word/letter size. The Chinese equivalent of this is 「識字量」.
Who tell you 词汇量 is a word, why is 汉字量 not a word?Both of them are same structure.
词汇量 = 词汇 + 量
汉字量 = 汉字 + 量
You can say both of them are two word to generate a new one.
As others have pointed out, the term that is currently in use is "识字量". However, @showkey has pointed out, 汉字量 is not inherently incorrect.
In fact language is an arbitrary thing. When a concept is first introduced into Chinese, what usually happens is that multiple different terms will be invented and used by different people. Eventually, people settle down on one single word. Hence the word "词汇" (vocabulary) has been variously called 语汇, 字汇, 辞汇 during history (see dictionary excerpt below). You might very well use "字汇量" to express the number of characters people recognize. It's just that due to historical coincidence people did not choose this word.
《近现代汉语辞源》p. 213 on the history of the term 词汇：
I reckon that's because 汉字 is a rather specific term that means (written) Chinese. It doesn't actually mean Chinese characters, per se. Therefore, applying 量 to 汉字 is a bit nonsensical.
As others already mentioned, here is a noun “识字量” for using，which means the quantity of knowing words."字" here specially point to Chinese character.
"汉字量” is more common used as abbreviation of "汉字数量", the quantity of whole Chinese characters.
words = 词汇,单词, for phonetic language generally, is basic unit in semantics. "词汇量" is used in spoken for phonetic language(distinguish from Chinese), which could be thought as abbreviation of "所识词汇量", omitted "所识" by default for convenient in spoken. And generally, it shouldn't omitted in serious literary language(written language).
character = 字, basic unit of semantics for Chinese.
