程度・範囲・強調N1
〜（で）すら
even... / (not) even...
Structure
N + すら／でさえ；N + にすら
Explanation
Even the extreme example (let alone others). More formal than さえ. Attached to nouns (＋で) or noun + にすら.
Examples
彼は自分の名前すら書けない。
He can't even write his own name.
忙しくて、食事をする時間すらなかった。
I was so busy I didn't even have time to eat.
Note
Synonymous with さえ/でさえ but more formal. In negatives: すら〜ない.
Related Grammar
〜さえ〜でさえ