noun which may take the genitive case particle 'no', noun
thoughtless; inconsiderate; unthinking
Describes a person or action lacking careful thought or consideration for others. Often used as a noun or with な/の to modify nouns.
His thoughtless remark hurt everyone.
If you act without thinking, you'll fail.
Standard kanji-kana spelling.
Alternate spelling using 無し for なし; less common but acceptable.
Compound of 考え (thought) + なし (without). The exact historical derivation is straightforward; the word is a transparent combination of its parts.