noun
unrequited love; one-sided love
Refers to romantic feelings that are not returned by the other person. Often used in literary or poetic contexts.
彼女への片恋に苦しんでいる。
I am suffering from unrequited love for her.
片恋の歌を詠む。
Compose a poem about one-sided love.
More common and colloquial term for unrequited love. 片恋 is more literary and less frequently used in everyday conversation.
Compound of 片 (kata, 'one side') and 恋 (koi, 'love'). The exact historical derivation is uncertain, but the meaning is transparent.