theorise vs speculate

theorise and speculate both are verbs.

Word	Noun	Adjective	Verb	Adverb
theorise	No	No	Yes	No
speculate	No	No	Yes	No

As verbs, theorise and speculate are synonyms defined as:

theorise and speculate: to believe especially on uncertain or tentative grounds

Other synonyms of theorise include conjecture, hypothecate, hypothesise, hypothesize, suppose, theorize.

theorise (verb)	speculate (verb)
to believe especially on uncertain or tentative grounds	reflect deeply on a subject
	to believe especially on uncertain or tentative grounds
	talk over conjecturally, or review in an idle or casual way and with an element of doubt or without sufficient reason to reach a conclusion
	invest at a risk