Which word best defines a state of great joy, delight, or love?

The word that best defines a state of great joy, delight, or love is "rapture." It specifically refers to an intense expression of happiness or ecstasy, often experienced during moments of profound appreciation or emotional fullness. The term evokes feelings of being transported by joy, making it the most appropriate choice for conveying deep emotional elation.

In contrast, "copious" describes something that is abundant or plentiful, but it does not relate to emotions or states of happiness. "Acrid" refers to a sharp or bitter taste or smell, which is also unrelated to feelings of joy or love. "Fastidious" denotes being very attentive to detail or hard to please, which again does not capture the essence of joy or delight. Therefore, "rapture" is the clear and fitting choice for representing a state of great joy.