Knife vs Dagger: What's the Difference? 

In german the distinction between a "Messer" (=knife) and a "Dagger" (=Dolch) is defined by the number of edges of the blade: anything with a single edge is called a "Messer", all double edged blades are a "Dolch" (=dagger). Nevertheless, a single edged rondel dagger will still be called a "ScheibenDOLCH", for the same reasons you mentioned: it is made for fighting and in this case it is defined by its purpose.

in Germany and Austria, there were different guilds for knife makers and sword makers. You were only allowed to produce products that are covered by the regulations of your guild. A sword (or dagger) was made by: Bladesmith (ger: Klingenschmied), Hiltmaker (ger: Gehilzmacher), Sharpener and polisher (ger: Schwertfeger). A knife was made by: the knifemaker (ger: Messerer). So boiled down to the essence, a knife was cheaper, because you only had to pay one person and not three, also you only paid guild fees one time and not three times.

Neat. I feel like the tool/weapon line gets especially blurry with things like the Bauernwehr.

Like many have said, daggers generally have a double edged blade. Many legal codes in the US distinguish Daggers (double-edged) and Dirks (single-edge) from knives (single-edge). I'm going to say that while most daggers, dirks and knives follow this convention, not all. I've never see a Bowie knife described as a dagger or dirk, but in most cases they are very clearly intended for fighting. Historically, some States, Territories, Cities banned the carry of Bowie knives, just as many still ban daggers and dirks (and Balisong/"Butterfly knives"). I'll add that I agree, daggers and dirks are primarily intended for stabbing, not cutting.

various daggers and swords were probably also used as tools as well when purpose built implements were not available

The same distinction in Dutch. Dolk= dagger and mes=messer=knife.

Otra duda es la diferencia entre daga y puñal.

Un cuchillo Bowie es un arma iconica para pelear, pero no es una daga.

Option of two fresh edges on blade.

some knives were designed based on swords but there are also some swords that were designed based on existing knives

I love my Koeln messer it’s a great fighting weapon

There is much wider variety of knives. From knives being tools in different trades, to hunting and letter opening :)

A dagger is designed primarily for dagging i.e. stabbing.

It different

Yay

There is a lot of historical context for why the English didnt like people eating w/ weapons. There is historical context for people being slaughtered while they eat & make merry we will say. Lol

🗿👍🏿

Nothing. It's semantics.