learning by heart; memorization
Refers to committing something to memory, often through repetition. Can imply rote learning.
Memorizing English words by rote is inefficient.
He memorized the textbook and took the exam.
faint memory; vague recollection
Used when one has only a dim or uncertain memory of something. Often contrasted with うろ覚え, which implies a hazy or unreliable memory.
See also: うろ覚え
I have only a faint memory of that story.
I answered from a vague recollection and got it wrong.
Standard kanji spelling.
Mixed kana-kanji spelling; less common but still used.
Compound of 空 (そら, 'empty, sky') and 覚え (おぼえ, 'memory, learning'). The exact semantic development is uncertain; 空 may imply 'by heart' (as if from the air) or 'vague' (as in empty/insubstantial).