theoretically

The word “theoretically” means in theory, though not necessarily true in practice. In plain terms, used to point out that something is possible or true only as an idea, not confirmed in reality.

Here is “theoretically” used in a sentence: “Theoretically, the plan should work, but we haven't tested it.”

“Theoretically” is an adverb.

“Theoretically” is an uncommon word in modern English.

Theoretically describes what should happen according to a theory or set of rules, regardless of real-world conditions, while technically points to a literal or strict interpretation of facts. "Theoretically, the plan should work" concerns expected outcomes, whereas "technically, it's still Tuesday" concerns exact fact.

Theoretically describes what is true in theory or in principle, while practically describes what actually happens once real-world factors come into play. Something can be theoretically possible yet practically very difficult or unlikely.

Yes, "theoretically" is commonly used as a sentence adverb to introduce a statement about what should be true in principle, as in "Theoretically, everyone should have received the email." This usage is standard in both spoken and written English.