na-adjective
young and sweet; innocent; adorable
Describes a child or young person who is endearingly innocent and sweet, often evoking a protective feeling.
いたいけな少女が花を摘んでいた。
An innocent little girl was picking flowers.
彼のいたいけな笑顔に心が和んだ。
His sweet, innocent smile warmed my heart.
na-adjective
Used when a young or vulnerable person's situation evokes pity or compassion; often implies they are unable to help themselves.
戦災で親を失ったいたいけな子供たち。
Pitiful children who lost their parents in the war disaster.
いたいけな姿を見て、思わず
Seeing his helpless figure, I couldn't help but want to help.
The exact derivation is uncertain. The kanji 幼 (young) and 気 (spirit/feeling) suggest a connection to youthful innocence, but the word is now almost always written in kana.