すると・
すると introduces the event, discovery, or conclusion that follows from the preceding situation. そうすると points back more explicitly to the action or assumption just mentioned.
What the connective does
すると moves the account forward. In a story, the first event is complete before the next event or discovery appears. In an explanation or conversation, the same form can introduce a conclusion that follows naturally from the information just given.
An event and an inference
The context normally makes it clear whether the second sentence reports what happened next or states what can now be concluded.
駅に着いた。すると、改札の前に長い列ができていた。
Upon arrival at the station, there was an unexpected sight: a long line had formed in front of the ticket gates.
AnalyzeThe second sentence presents a discovery made after the arrival.
会議は三時に始まり、二時間の予定です。すると、終了は五時ごろですね。
The meeting starts at three and is scheduled to last two hours. So it should finish around five, then.
AnalyzeThe finishing time is inferred from the schedule.
Why the longer form is useful
そうすると contains an explicit “doing so” idea. It is especially useful when the speaker wants to point back to a proposed action, procedure, or assumption before stating its consequence. The distinction is a matter of emphasis rather than a rigid rule.
まず、申込書を保存してください。そうすると、確認画面に進めます。
First, save the application form. Once you do that, you can proceed to the confirmation screen.
AnalyzeA result versus a chosen response
すると commonly narrates or infers what follows. By contrast, それなら accepts the preceding information as a condition and often introduces the speaker’s decision or proposal.
明日は休館です。それなら、金曜日に行きます。
It is closed tomorrow. In that case, I will go on Friday.
AnalyzeThe second sentence is a chosen response, not an event that simply follows.
More examples
窓を開けた。すると、冷たい風が入ってきた。
The window was opened, and then a cold wind came in.
Analyze彼女がベルを鳴らした。すると、奥から店員が出てきた。
She rang the bell. Then a clerk came out from the back.
Analyze橋を渡り終えた。すると、急に海が見えた。
After crossing the bridge, the sea suddenly came into view.
Analyze九ページまで読みました。資料は全部で十二ページです。すると、残りは三ページですね。
Nine pages have been read, and the document has twelve pages in total. So there are three pages left.
Analyzeこの部品を外します。そうすると、中の電池を交換できます。
Remove this part. Once that is done, the battery inside can be replaced.
Analyzeこのクラスは二十人で、今日は全員出席です。すると、出席者は二十人ですね。
This class has twenty students, and everyone is present today. So there are twenty people in attendance.
Analyze来月から家賃が一万円上がるんですか。そうすると、年間で十二万円増えることになりますね。
The rent is going up by ten thousand yen a month starting next month? In that case, that means an increase of 120,000 yen a year.
Analyze