sehr adv.
Zum Beispiel:
Es schmeckt mir sehr.
Bill Gates ist sehr reich.
viel indef. pronoun, adj.
Zum Beispiel:
Das Kind hat viel gegessen.
Bill Gates hat viel Geld.
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Sign up to join this communityYou answered the question yourself by indicating the function of the words. "Sehr" is an adverb and as such it modifies adjectives, verbs or other adverbs.
Das Haus ist sehr hoch.
Ich laufe sehr schnell.
Das missfällt mir sehr.
"Viel" is a pronoun and as such it stands in for persons or things.
Ich habe viel gegessen.
You could replace it with "Pizza" or "it" if you want to. "Viel" can also be an adjective that modifies or kind of "counts" nouns.
Jan hat viel Geld.
The two are never interchangeable. The confusion mainly comes from the fact that they can be both a translation for the English "a lot"
Jan has a lot of money.
Melanie likes that a lot.
sehr
as an adverb for verbs is very rare. It's only common for verbs meaning affection like mögen
, lieben
, hassen
…. In the case of arbeiten
, both sehr
and viel
are possible. Ich arbeite viel.
means I work a lot.
. Ich arbeite sehr.
means I'm working intensively.
with the details of this intenity unclear (which is why it's rarely used). In the case of laufen
only viel
is usually possible. Maybe, if you want to describe a certain point in a spectrum of movements from walking to running not characterized by velocity, you could use sehr laufen
.
sehr = very, viel(e) = a lot / much /many
"Viel" is associated with number. You can count how much money Bill has, you can count (sort of) how much the child ate.
"Sehr" is an amplifier, like 'very' in English.
Compare:
"Ich habe heute viel gelernt." - I have learned much today.
"Ich habe heute sehr viel gelernt." - I have learned very much today.
sehr
makes sehr
also associated to numbers.
sehr
on its own in this construction, because you would end up with I have learned very today
.