How can I know whether a word is countable or uncountable? I did not find that in Duden or the dict.cc dictionary. Is that same as in English? For example, in English, the word "information" is uncountable but I see in German "viele Informationen", that means "Information" in German is countable ("viele").
Duden will tell you, in the »Bedeutungen« section,
Grammatik: ohne Plural
Towards the end of the article there is a separate »Grammatik« section which will nearly always list a plural because there is some special case in which a usually uncountable noun will have a plural:
Glück: die Glücke (Plural selten) – see meaning 3b, various lucky or happy events
Milch: (Fachsprache:) Milche[n] – different kinds of milk, e.g. mother's milk vs. cow milk
Zucker: (Sorten:) Zucker – different kinds of sugar
There might be uncountable nouns which are always uncountable in German and I assume these will be marked as such in the Duden.
An extreme case of plurallessness is Jura, which doesn’t even have an article, let alone a plural. But again, this is not explicitly stated.
Wiktionary covers fewer meanings of »Glück« than Duden, none of which have a plural, and is stated there
Worttrennung: Glück, kein Plural
What you are referring to, is the decision, whether something is a singularetantum. While in principle I see no difference to English, you have to look it up.
This property is a convention, which sometimes changes over times. The example Information is an interesting one, since it can be a unit (so you may just have little or much of it; one would measure that in bit) or considered countable indicating separate facts.
Verbrauch is another example; nobody would have used that in plural some decades ago, but would have used Verbrauchswerte (e. g. fuel consumption of a car in town and across the country environment). Unglücke made a similar transition, now refering to separate countable desasters and no longer restricts to the opposite of Glück. Arbeit also has meanings differing in respect to countability: the amount of work to do in your job is not countable, but (e.g. in school or output of artists) when representing a separate countable test or piece of art countability applies.
The linked page list these general suspects:
- Abstract nouns: Friede, Glanz, Spott
- substance names: Gold, Heu, Milch
- nominalisations: das Laufen, Gemütlichkeit
- category names: Getreide, Publikum, Obst
- portionable stuff: Regen, Lärm, Nässe
- uniques: Weltall, Mona Lisa, Parthenon