Comparing using a noun vs comparing using an adjective

Question

In one of my recent posts on r/Writestreakgerman (subreddit), I got the following statement corrected as the statement written underneath it.

Meine Tage sind mehr Produktiv als vorher, weil ich mehr Zeit habe. (me)

Meine Tage sind produktiver als vorher, weil ich mehr Zeit habe.

Why was the adjective used to compare rather than the noun?

For comparison, in English, the first would be correct syntatically:

My days are more productive than before, because I have more time

Answer 1

You base assumption that "productive" or "produktiv" respectively is a noun in either English or German is faulty. In both languages the form of the sentence you use requires the use of an adjective in the comparative form:

productive - more productive - most productive (adj). productivity (noun).

produktiv - produktiver - am produktivsten (Adj). die Produktivität (Subst.)

German knows only one way to change an adjective into the comparative and superlative form (like above). English has two ways to do so - which depends on the length of the adjective in syllables. Shorter English adjectives use a form more similar to the German way:

nice - nicer - nicest (adj).

Answer 2

German and English form comparatives (and also superlatives) differently.

English adds -er to short adjectives and uses more for long adjectives.

German always adds -er, it doesn't use mehr to form the comparative. While English more generally translates to German mehr, this does not apply to the comparative.

That's why it has to be produktiver, not mehr produktiv.

Apart from that, even if mehr produktiv were valid, produktiv would have to be lowercase, because it is not a noun.

Answer 3

I don't care for a moment, how to build the correct comparative in German. (I'll come to that later.)

1. How to test, if a word is a noun or an adjective?

   This is relatively simple: replace the word in question with other words where you know for sure whether they are nouns or adjectives. If you get a sentence that still makes sense (although it has a different meaning, of course), then the word in question belongs to the same part of speech. (Not making sense doesn't mean anything, just try another word).

   Names of things are nouns. Tree (Baum), stone (Stein), stick (Stab) etc. are nouns.

   Properties of things are adjectives. Green (grün), hard (hart), long (lang) etc. are adjectives.

   Here is your sentence (without the subordinate clause, which is not relevant here):

   Meine Tage sind mehr (P|p)roduktiv als vorher.
   My days are more productive than before.

   • Is it a noun?

     Meine Tage sind mehr Baum als vorher.
     My days are more tree than before.

     Meine Tage sind mehr Stein als vorher.
     My days are more stone than before.

     Meine Tage sind mehr Stab als vorher.
     My days are more stick than before.

     None of these sentences does make sense. So let's try some adjectives:

   • Is it an adjective?

     Meine Tage sind mehr grün als vorher.
     My days are more green than before.

     Meine Tage sind mehr hart als vorher.
     My days are more hard than before.

     Meine Tage sind mehr lang als vorher.
     My days are more long than before.

     The first sentence does not really make sense, but still it feels better in some way than the sentences before. But the last two sentences make sense (although they still are grammatically wrong, and this in both languages). And this means, that the English word »productive« and the German word »produktiv« are both adjectives. And in German this also means, that is has to be written with a lowercase first letter (except when it's the first word of a sentence.)

   Meine Tage sind mehr produktiv als vorher.

2. How to build the comparative of an adjective in German?

   This sentence is wrong in English:

   My days are more long than before.

   But this is correct:

   My days are longer than before.

   This is because in English, the comparative of an adjective with only one syllable is built by adding -er to the end: fast → faster, old → older, long → longer. (In some cases you need additional changes, like doubling the last consonant in hot → hotter). For adjectives with three and more syllable there is another mechanism: add the word »more« before the adjective: expensive → more expensive, incomprehensible → more incomprehensible. (For adjectives with two syllables both versions are in use: thirsty → thirstier, open → more open.)

   But German does not have two mechanisms for this job. It has just one: add -er to the end (and sometimes do also some other changes, like turning a normal vowel into an umlaut).

   English positive	English comparative	German positive	German comparative
   fast	faster	schnell	schneller
   old	older	alt	älter
   long	longer	lang	länger
   hot	hotter	heiß	heißer
   expensive	more expensive	teuer	teurer
   incomprehensible	more incomprehensible	unverständlich	unverständlicher
   thirsty	thirstier	durstig	durstiger
   open	more open	offen	offener
   productive	more productive	produktiv	produktiver

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Summary

We began here

Meine Tage sind mehr Produktiv als vorher.

Then we learned, that this word is not a noun but an adjective, so it has to be written with a lowercase first letter:

Meine Tage sind mehr produktiv als vorher.

And then we learned, that the mechanism »"mehr" + adjective« does not exist in German. Instead it's always »adjective+"er"«.

Meine Tage sind produktiver als vorher.