Lassen = Let/Leave

Easy Peesy

The verbs "to leave" and "to let" correspond to "lassen," which explains the existence of "leave him be" beside the more standard "let him be."

"lassen" in German has several distinct functions.

1) "lassen" means "to leave (behind); to allow to remain in a place or condition."

This action can be on purpose or accidental.

It always requires an object or other complement (as opposed to the English "let's leave"):

Ich lasse das Kind bei meinen Eltern.	I am leaving the child with my parents.
Lässt du den Wagen hier?	Are you leaving the car here?
Sie ließ ihre Brille im Wagen.	She left her glasses in the car.
Lassen Sie einfach alles auf.	Just leave everything open.
Lassen Sie mich in Ruhe.	Leave me in peace.
Sie hat ihr Buch im Büro gelassen.	She left her book at the office.
Sie lässt die Stadt hinter sich.	She is leaving the city behind.
Wir lassen alles beim Alten.	We're leaving everything as it was.
Der Film ließ mich kalt.	The film left me cold.

It can also be combined with other verbs (stehen lassen, sitzen lassen, liegen lassen) as if it were a modal auxiliary.

Often it carries special meanings.

Ich ließ den Wagen in der Garage stehen.	I left my car (standing) in the garage ["stehen lassen" is often used in this sense for things that cannot be carried].
Sie ließen mich im Regen stehen.	They left me in the rain [abandoned me; left me stranded]
Er hat sie sitzen lassen.	He jilted her.
Du hast mich mit den Kindern sitzen lassen.	You left me to take care of the children.
Sie lässt alles liegen.	She's leaving everything as is [in order to do something else]

2) "lassen" also means: "to let, permit, or cause someone else to do something:"

Wir lassen ihn fahren.	We're letting him drive.
Ich ließ sie etwas anderes machen.	I let her do something else.
Sollen wir ein Taxi rufen lassen?	Should we have someone call a taxi?
Lässt du ein Haus bauen?	Are you having a house built?
Er hat sein Referat von einem anderen Studenten schreiben lassen.	He had his paper written by another student.

3) "sich lassen" can be used instead of the passive voice, often implying "können:"

Der Wagen lässt sich leicht reparieren.	The car is easy to repair/can be repaired easily.
Das lässt sich hoffen.	That is to be hoped.
Mit Geld lässt sich alles regeln.	With money you can arrange anything.

4) It is also possible to use "lassen" for imperatives that combine the first and second person, corresponding in structure to the English "let's...."

The form of "lassen" reflects whether one other person is being addressed or more than one, as well as whether or not the speaker uses the familiar or formal pronouns with the addressee(s):

Lass uns gehen.	Let's go.
Lasst uns beten.	Let us pray.
Lassen Sie uns morgen schwimmen gehen.	Let's go swimming tomorrow.

5) Some other special uses of "lassen:"

Das lasse ich mir nicht gefallen.	I won't put up with that.
Er lässt sich alles gefallen.	He'll put up with anything.
Er lässt gerne auf sich warten.	He doesn't mind making you wait (It's typical of him to keep us waiting).
Lass dir das eine Warnung sein.	Let that be a warning to you.
Mein Vater lässt grüßen.	My father sends his greetings.
Er hat sich nicht anmerken lassen, was er denkt.	He didn't let show what he thinks.
Lassen Sie uns wissen, wie es Ihnen geht.	Let us know how you're doing.
Lass ihn nur kommen.	Just let him come [I'll deal with him].
Lassen Sie mal von sich hören.	Get in touch sometime.
Wir ließen den Arzt kommen.	We sent for the doctor.
Lassen Sie mal sehen.	Let's have a look.
Ihre Antwort lässt mich glauben, dass sie nichts verstanden hat.	Her answer leads me to believe that she didn't understand anything.
Der Professor lässt das Buch herumgehen.	The professor passes the book around (the table/the room).