Learn Hardcore German: Die Tatsache bleibt: Ohne Übung ist Grammatik schwer zu behalten. - The fact remains: without practice grammar is hard to retain.

Bleibt means “remains,” so Die Tatsache bleibt conveys persistence: the fact continues to be true. With Die Tatsache ist, you just state a fact; with bleibt, you stress that it stays true despite circumstances.

Why is there a colon after Die Tatsache bleibt? Could it be a comma?

The colon introduces the content of the “fact.” It’s a stylistic way to foreground the conclusion. You could also write a dass-clause with a comma: Die Tatsache bleibt, dass Grammatik ohne Übung schwer zu behalten ist. Both are correct; the colon keeps the following clause in main-clause (V2) order.

Why does ist come before Grammatik after starting with Ohne Übung?

German main clauses follow the V2 rule: the finite verb is in second position. The fronted prepositional phrase Ohne Übung occupies the first position, so the verb ist must come next, and the subject Grammatik follows: Ohne Übung | ist | Grammatik ...

What case does ohne take, and what does that mean for Übung?

Ohne always takes the accusative. Here, Übung is feminine singular and looks the same in nominative and accusative, so you don’t see a change. In the plural you would see it: ohne Übungen.

Why is there no article before Grammatik? Could I say die Grammatik?

Abstract or field-of-study nouns often appear without an article in general statements: Grammatik ist ... Using die Grammatik can also be correct, especially if you mean a specific grammar (e.g., of a particular language) or “grammar” as a system: Die Grammatik des Deutschen ist ... In your sentence, both are possible; the bare form feels a bit more general.

Why are Tatsache, Übung, and Grammatik capitalized?

All common nouns are capitalized in German. Tatsache, Übung, and Grammatik are nouns; ohne and bleibt are not.

Is there a difference between schwer and schwierig here?

Both can mean “difficult,” and both work here. Schwer is very common and slightly more colloquial; schwierig can sound a bit more formal or suggest “complicated.” Nuance is mild in this context.

How does the pattern schwer zu + infinitive work?

It’s an adjective + zu + infinitive construction meaning “hard/easy to do”:

schwer zu behalten = “hard to retain”
leicht zu verstehen = “easy to understand”
The zu belongs to the infinitive and sits right before it (or inside it for separable verbs; see next answer).

Where does zu go with separable verbs?

With separable verbs, zu goes between the prefix and the stem: aufzuschreiben (from aufschreiben), fernzusehen (from fernsehen). Behalten is not separable, so it stays zu behalten.

Who is the “doer” in Grammatik ist schwer zu behalten?

Semantically, a learner is doing the retaining, but German uses an impersonal evaluative structure (“X is hard to do”). You can paraphrase it as Es ist schwer, Grammatik zu behalten, where es is a dummy subject and Grammatik is the object of behalten.

Are there alternative word orders that are equally correct?

Yes:

Grammatik ist ohne Übung schwer zu behalten.
Es ist ohne Übung schwer, Grammatik zu behalten. All are natural; fronting Ohne Übung just emphasizes the condition.

Does Übung mean “practice” or “exercise”?

Both, depending on context. Here, Ohne Übung means “without practice” (training/repetition). In a textbook, Übungen often means “exercises” (tasks).

Why use behalten and not lernen or (sich) merken?

behalten = to retain/keep in memory over time.
lernen = to learn/acquire knowledge.
(sich) merken = to notice and commit to memory (“to remember/memorize”).
Your sentence talks about long-term retention, so behalten is apt. You could also say Grammatik ist ohne Übung schwer sich zu merken, but that slightly shifts the nuance to memorizing.

Should schwer have an ending here?

No. After sein in predicate position, adjectives are uninflected: ist schwer. With a noun, you’d inflect: eine schwere Übung.

Should there be a comma after Ohne Übung?

No comma is required. German sets commas mainly between clauses, not after a simple fronted adverbial like Ohne Übung.

Can I say ohne zu üben instead of ohne Übung?

You can, but mind subject alignment. Ohne zu üben ist Grammatik schwer zu behalten is awkward because Grammatik can’t be the subject of üben. Better: Ohne zu üben ist es schwer, Grammatik zu behalten. Here es is a dummy subject.

What are the genders and plurals of the nouns here?

die Tatsache (f.), plural die Tatsachen
die Übung (f.), plural die Übungen
die Grammatik (f.), plural die Grammatiken (rare; usually the singular means the discipline/system)

Is Fakt interchangeable with Tatsache in Die Tatsache bleibt?

Often yes in meaning, but the phrase Die Tatsache bleibt is a set, idiomatic expression. Der Fakt bleibt is understood but sounds less idiomatic/formal than Die Tatsache bleibt.