sheer
v.v. used to emphasize the size or degree of something, meaning 'complete' or 'nothing but'.
v. serving to emphasize the size, degree, or amount of a quality; absolute or unmitigated.
Winning the lottery is sheer luck.
The project succeeded through sheer determination, not because it was easy.
The sheer scale of the disaster overwhelmed the emergency services, which were unprepared for a crisis of that magnitude.
From Middle English shere, scheere, schere, skere, from Old English sċǣre (“pure, sheer; shining, clear”), from Proto-Germanic skairiz; supplanted the semantically close shire (dialectal), from Middle English schyre, schire, shire, shir, from Old English sċīr (“clear, bright; brilliant, gleaming, shining, splendid, resplendent; pure”), beside which existed Middle English skyr, from Old Norse skírr (“pure, bright, clear”), both from Proto-Germanic skīriz (“pure, sheer”), from Proto-Indo-European *(s)ḱeh₁y- (“luster, gloss, shadow”). Cognate with Danish skær, German schier (“sheer”), German Low German schier (“sheer, pure, unadulterated”; “completely, almost”), Dutch schier (“almost”), Gothic 𐍃𐌺𐌴𐌹𐍂𐍃 (skeirs, “clear, lucid”). Outside Germanic, cognate to Albanian hir (“grace, beauty; goodwill”).
Perhaps from Dutch scheren (“to move aside, skim”); see also shear.
The adjective is almost always used prenominally, meaning it comes directly before the noun it modifies.
His determination was sheer.It was sheer determination.Sheer is a prenominal adjective and is not used predicatively (after the noun or a linking verb like 'is').