assumption, guess
C'est une simple supposition, n'est-ce pas ?
It's just a guess, isn't it?
C'est une supposition, pas un fait.
It's an assumption, not a fact.
Mais votre supposition était en partie juste.
But your assumption was partly right.
— Full River Red (2023)
Une supposition, d'après ce que j'ai appris dans ma mémoire.
A guess, based on what I remember learning.
— The Man from Earth (2007)
It's pure speculation.
Sa supposition se révéla juste.
His guess turned out to be correct.
It's just a guess.
That was my guess.
Votre supposition est aussi bonne que la mienne.
Your guess is as good as mine.
Pure supposition, tu n'as aucune preuve solide.
Pure speculation—you have no solid evidence.
— Ghost in the Shell (1995)