Solitary means being alone or being the only one.
Being solitary can feel peaceful or lonely, depending on the situation.
Examples:
The solitary tree stood alone in the field.
She prefers solitary activities like reading and drawing.
The cat is solitary and doesn't like other cats.
The solitary cookie left in the jar was calling my name.
In the deep, dark forest, there lives a solitary wolf.
He enjoys the solitary quiet of the library.