Schließen vs. verschließen
The German verbs schließen and verschließen both relate to the act of closing, but they are not interchangeable. The main difference lies in the degree of finality and security, with verschließen being the stronger and more specific term emphasizing the act of locking or sealing.
Schließen
A1This is the general and most common verb for to close. It describes the simple action of moving something (like a door or a book) to a closed state. It can also be used abstractly to mean to conclude or to finish (a meeting, a contract) or to infer.
Kannst du bitte das Fenster schließen? Es zieht.
(Can you please close the window? It's drafty.)
Der Supermarkt schließt um 22 Uhr.
(The supermarket closes at 10 PM.)
Sie schloss die Augen und schlief sofort ein.
(She closed her eyes and fell asleep immediately.)
Wir haben den Vertrag letzte Woche geschlossen.
(We concluded the contract last week.)
Aus seinem Schweigen schließe ich, dass er einverstanden ist.
(From his silence, I infer that he agrees.)
Verschließen
A2This verb means to lock, to seal, or to close securely. It implies an additional action beyond simply closing to make something inaccessible, often involving a key, a lock, or a tight seal.
Vergiss nicht, die Haustür zu verschließen, wenn du gehst.
(Don't forget to lock the front door when you leave.)
Die Kekse müssen in einer Dose gut verschlossen werden, damit sie frisch bleiben.
(The cookies must be sealed well in a tin so that they stay fresh.)
Er verschloss die wichtigen Dokumente im Tresor.
(He locked the important documents in the safe.)
Nach der Enttäuschung hat er sein Herz verschlossen.
(After the disappointment, he closed off his heart.)
Das Kind verschloss die Augen vor dem unheimlichen Geräusch.
(The child shut its eyes tightly at the scary noise.)
Summary
In essence, use schließen for the general act of closing something (a door, a shop, a book). A simple rule is: if you can do it without a key or lock, it's probably schließen. Use verschließen when you specifically mean to lock or to seal something to make it secure and inaccessible. Furthermore, only schließen has the additional meanings of to conclude or to infer.