conjecture
US /kənˈdʒek.tʃɚ/
UK /kənˈdʒek.tʃɚ/

1.
an opinion or conclusion formed on the basis of incomplete information
:
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The detective's theory was based on conjecture, not solid evidence.
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His statement was pure conjecture, without any factual basis.
1.
form an opinion or conclusion on the basis of incomplete information
:
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We can only conjecture about the true cause of the accident.
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Based on the limited data, I conjecture that the market will recover soon.