der Stoß
push / jolt
A short, forceful movement in which someone or something is pushed. It can also refer to an impact or a shock.
Er bekam einen Stoß von hinten und fiel die Treppe hinunter.
He got a push from behind and fell down the stairs.

push / stack / collision
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push / jolt
A short, forceful movement in which someone or something is pushed. It can also refer to an impact or a shock.
Er bekam einen Stoß von hinten und fiel die Treppe hinunter.
He got a push from behind and fell down the stairs.

The noun 'der Stoß' (push, jolt) is derived directly from the strong verb 'stoßen' (to push, bump). It describes the action or result of pushing or bumping.
Pass auf, dass du dich nicht am Tisch stößt!
Be careful not to bump into the table!
The meanings are easy to distinguish from context. A 'Stoß' (push, jolt) as a movement (meaning 1) happens between people or objects. A 'Stoß' (stack, pile) as a stack (meaning 2) almost always refers to paper, files, or books.
Er gab mir einen leichten Stoß, um meine Aufmerksamkeit zu bekommen.
He gave me a slight push to get my attention.
For the movement, the verbs 'geben' (to give) and 'bekommen' (to get) are often used. You can say 'jemandem einen Stoß geben' (to give someone a push) or 'einen Stoß bekommen' (to get a push).
Im vollen Bus habe ich aus Versehen einen Stoß bekommen.
On the crowded bus, I accidentally got pushed.
When 'Stoß' (stack, pile) means a stack, it is often specified what it consists of. This is usually done with the genitive or with 'von' (of): 'ein Stoß Papiere' (a stack of papers) or 'ein Stoß von Büchern' (a stack of books).
Auf dem Boden lag ein großer Stoß alter Zeitungen.
There was a large stack of old newspapers on the floor.
The meaning 'Kollision' (collision) is a technical term from physics. In normal everyday life, 'Stoß' is not used in this sense.
Im Physikunterricht haben wir den elastischen Stoß berechnet.
In physics class, we calculated the elastic collision.
blow / stroke
'der Schlag' and 'der Stoß' both describe a short, forceful movement against someone or something. 'der Schlag' is more like a blow or hit, often with the hand, a stick, or another object. 'der Stoß' is more like a pushing or shoving movement, where someone or something is moved forward or to the side. Learners may confuse the words because both can be sudden and forceful. In practical terms: you use 'schlagen' for a quick striking movement; you use 'stoßen' when you push something away or bump into someone.

Im Bus bekam Mehmet einen Stoß von hinten und verlor fast das Gleichgewicht.
On the bus, Mehmet got a shove from behind and almost lost his balance.
Der Schlag mit dem Hammer traf den Nagel genau in der Mitte.
The blow with the hammer hit the nail exactly in the middle.