What it means
要するに means “in short” or “to sum up.” It introduces a concise statement that restates the main point of a preceding explanation, set of facts, or series of events. It commonly appears at the beginning of a sentence and signals that the speaker is simplifying or drawing together information rather than adding a new detail.
Usage note
要するに is neutral in register, but the clause that follows it must be changed separately for familiar or polite speech. It summarizes information that has already been presented, so using it without any preceding context can sound abrupt.
How to use it
要するに、Clause (plain form)
要するに、会議は中止です。
In short, the meeting is canceled.
要するに、Clause (plain form)
要するに、会議は中止だ。
In short, the meeting is canceled.