What's the adjective for companionless? Here's the word you're looking for.
Included below are past participle and present participle forms for the
verbs companion and compane which may be used as adjectives within certain contexts.
“What a strange life of privation, thought I, alone and companionless as he must be!”
“Eventually, even this zombie of a star rests in peace. At least, this is what happens to a pulsar that is the remains of a lonely, companionless star such as the sun.”
“Sitting companionless at a table patently designed for four, I composed the portrait of my meal with some care, both to entice my viewers and to deride my circumstances.”
