简要结论
“Knowledge” 是一个 不可数名词，通常不能直接加复数形式（如 “knowledges”），也不能与不定冠词 “a” 连用（如 “a knowledge”）。
✅ 正确：She has deep knowledge of history.
❌ 错误：She has a deep knowledge of history.（除非在特定固定表达中）
❌ 错误：She has a deep knowledge of history.（除非在特定固定表达中）
为什么 “knowledge” 不可数？
“Knowledge” 表示的是抽象概念——一个人所掌握的信息、理解或认知的总和。这类抽象名词（如 information, advice, happiness）在英语中通常被视为不可数。
不可数名词没有复数形式，也不能直接与数字连用。
常见正确用法示例
• He has extensive knowledge of computer programming.
• Her knowledge about ancient cultures is impressive.
• This course will increase your knowledge of biology.
• Her knowledge about ancient cultures is impressive.
• This course will increase your knowledge of biology.
特殊情况与固定搭配
虽然 “knowledge” 本身不可数，但在某些固定短语中，可能会看到类似 “a knowledge of...” 的结构。这种用法较为正式或文学化，现代英语中更推荐省略 “a”。
• (较正式) He has a thorough knowledge of French literature.
• (更自然) He has thorough knowledge of French literature.
• (更自然) He has thorough knowledge of French literature.
此外，在学术或哲学语境中，有时会用 “knowledges” 表示不同文化或体系下的“知识体系”，但这属于非常专业的用法，日常交流中应避免。
如何正确修饰 “knowledge”？
由于不可数，我们使用以下量词或形容词来描述 “knowledge”：
- a piece of knowledge（一条知识）
- deep / broad / vast / practical knowledge
- knowledge in / of / about [某领域]
• This book contains many useful pieces of knowledge.
• She has broad knowledge in environmental science.
• She has broad knowledge in environmental science.
常见错误纠正
❌ I learned many new knowledges today.
✅ I learned many new facts / pieces of knowledge today.
❌ She has a good knowledge.
✅ She has good knowledge of chemistry.
✅ I learned many new facts / pieces of knowledge today.
❌ She has a good knowledge.
✅ She has good knowledge of chemistry.