つまりIn short, To sum up, In other words

つまり and 要するに both signal a rephrasing or summary, often translated as 'in other words' or 'to sum up'. つまり is more casual and common in conversation, e.g. つまり、行かないってこと？ ('So, you're not going?'). 要するに is more formal and often used in writing or speeches, e.g. 要するに無理だということです ('To sum up, it's impossible').

つまり and ということは both rephrase earlier information, but differ in usage. つまり restates or explains something just said, e.g. つまりできないってこと？ ('So you're saying you can't do it?'). ということは introduces a logical inference or consequence, e.g. ということは、試合は中止だね ('So that means the game is canceled').

Both つまり and 即ち mean 'in other words', but differ in tone and context. つまり is casual and used in conversation, e.g. つまりしょうがないってこと ('In other words, it can't be helped'). 即ち is formal and often used in academic or written contexts, e.g. 生きることは即ち戦いである ('To live is, in other words, a battle').