na-adjective, noun, noun, used as a suffix
single-minded; wholehearted; earnest
Describes a person or attitude that is completely focused on one thing, often with a nuance of stubborn or unwavering devotion. Can be used as a noun, adjectival noun, or suffix.
彼は一途に彼女を愛している。
He loves her wholeheartedly.
一途な性格が彼
His single-minded nature is his strength.
ひたむき also means single-minded or earnest, but emphasizes steady, diligent effort toward a goal, while 一途 often implies an intense, sometimes narrow-minded devotion.
一筋 means 'one straight line' and figuratively 'single-mindedly devoted to one path', similar to 一途, but 一途 can carry a stronger emotional charge of being absorbed or obsessed.
Composed of 一 (one) and 途 (way, path), literally 'one path'. The meaning 'single-minded' derives from the idea of following a single path without deviation. The reading いちず is a regular on'yomi combination.