The act of making a supposition.

if hypothetically (optionally followed by that)

Capable of being supposed; imaginable

(nonstandard) supposedly

Able to be supposed or conjectured. / (nonstandard) Supposedly.

plural of supposal

The act of supposing; supposition. / Something supposed; a supposition, a hypothesis.

plural of supposing

The quality of being supposable.

(formal) Used to introduce a question, implying that eliciting an affirmative answer from the interlocutor would be unlikely yet desirable for the speaker.