noun, noun which may take the genitive case particle 'no'
ignorance; stupidity; ignorant person; stupid person
Refers to a lack of knowledge or common sense, often used critically or self-deprecatingly. Can describe a person or the quality itself.
あんなことを言うなんて、彼はまったくの物知らずだ。
Saying something like that, he is completely ignorant.
物知らずで恥をかいた。
I embarrassed myself because of my ignorance.
無知 is a more formal, Sino-Japanese word for ignorance or lack of knowledge, often used in serious contexts. 物知らず is more colloquial and can carry a nuance of lacking common sense or being naive.
馬鹿 is a stronger, more direct insult meaning 'fool' or 'idiot', while 物知らず is milder and focuses on ignorance rather than general stupidity.
Compound of 物 (thing) + 知らず (negative of 知る, to know), literally 'not knowing things'. The exact historical derivation is straightforward.