entweichen
to leak
For gases, liquids, or air: to come out or flow out of a container or an enclosed space.
Aus dem undichten Reifen ist langsam die Luft entwichen.
Air slowly leaked out of the punctured tire.

to escape / to leak
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to leak
For gases, liquids, or air: to come out or flow out of a container or an enclosed space.
Aus dem undichten Reifen ist langsam die Luft entwichen.
Air slowly leaked out of the punctured tire.

'Entweichen' (to escape / to leak) is an inseparable verb with the prefix 'ent-'. The prefix remains firmly attached to the verb 'weichen' (to yield / give way) in all sentence forms and indicates movement 'away from something'.
Er bemerkte, dass Gas aus dem Ofen entwich.
He noticed that gas was escaping from the stove.
Since 'entweichen' (to escape / to leak) describes movement or a change of state, the perfect tense is always formed with the auxiliary verb 'sein' (to be). The past participle is 'entwichen'.
Die ganze Luft ist aus dem Ballon entwichen.
All the air has leaked out of the balloon.
To indicate the place of origin from which something escapes or leaks, the preposition 'aus' (from / out of) with the dative is almost always used.
Rauch entwich aus dem Schornstein.
Smoke escaped from the chimney.
The meaning can easily be recognized from the subject. If it refers to gases, liquids, or air, it means flowing out or leaking. If it refers to people or animals, it means escape.
Aus der Flasche entwich ein seltsamer Geruch.
A strange smell escaped from the bottle.
When 'entweichen' (to escape) is used for people or animals, it often sounds elevated, literary, or official. It emphasizes secretly disappearing unnoticed.
Der Dieb entwich durch ein offenes Fenster in der Dunkelheit.
The thief escaped through an open window into the darkness.
to flee
'fliehen' and 'entweichen' can both mean that a person or animal leaves a place in order to get away. 'fliehen' is the normal word for people in danger or under pressure. 'entweichen' sounds rather elevated or literary when used for people or animals, and often emphasizes that someone escapes unnoticed. In everyday language, you almost always say 'fliehen'. 'entweichen' fits more in reports, stories, or when talking about animals, especially if the escape seems quieter or more secretive.

Dem Tier gelang es, aus dem Käfig zu entweichen.
The animal managed to escape from the cage.
Bei dem Unfall konnten alle Fahrgäste rechtzeitig aus dem Bus fliehen.
In the accident, all the passengers were able to flee from the bus in time.